Pull bpf updates from Alexei Starovoitov:
"Major changes:
- Recover from BPF arena page faults using a scratch page and add
ptep_try_set() for lockless empty-slot installs on x86 and arm64.
This allows BPF kfuncs to access arena pointers directly.
The 'arena_direct_access' stable branch was created for this work
and was pulled into sched-ext and bpf-next trees (Tejun Heo, Kumar
Kartikeya Dwivedi)
- Lift old restriction and support 6+ arguments in BPF programs and
kfuncs on x86 and arm64 (Yonghong Song, Puranjay Mohan)
Other features and fixes:
- Add 24-bit BTF vlen and reclaim unused bits in the BTF UAPI to ease
addition of new BTF kinds (Alan Maguire)
- Raise the maximum BPF call chain depth from 8 to 16 frames (Alexei
Starovoitov)
- Refactor object relationship tracking in the verifier and fix a
dynptr use-after-free bug (Amery Hung)
- Harden the signed program loader and reject exclusive maps as inner
maps (Daniel Borkmann)
- Replace the verifier min/max bounds fields with a circular number
(cnum) representation and improve 32->64 bit range refinements
(Eduard Zingerman)
- Introduce the arena library and runtime (libarena) with a buddy
allocator, rbtree and SPMC queue data structures, ASAN support and
a parallel test harness. Allow subprograms to return arena pointers
and switch to a BTF type-tag based __arena annotation (Emil
Tsalapatis)
- Cache build IDs in the sleepable stackmap path and avoid faultable
build ID reads under mm locks (Ihor Solodrai)
- Introduce the tracing_multi link to attach a single BPF program to
many kernel functions at once. Allow specifying the uprobe_multi
target via FD (Jiri Olsa)
- Extend the bpf_list family of kfuncs with bpf_list_add/del(), and
bpf_list_is_first/is_last/empty() (Kaitao Cheng)
- Extend the BPF syscall with common attributes support for
prog_load, btf_load and map_create (Leon Hwang)
- Wrap rhashtable as BPF map (Mykyta Yatsenko, Herbert Xu)
- Add sleepable support for tracepoint programs and fix deadlocks in
LRU map due to NMI reentry (Mykyta Yatsenko)
- Fix OOB access in bpf_flow_keys, fix nullness analysis of inner
arrays, enforce write checks for global subprograms (Nuoqi Gui)
- Report the maximum combined stack depth and print a breakdown of
instructions processed per subprogram (Paul Chaignon)
- Add an XDP load-balancer benchmark and arm64 JIT support for stack
arguments (Puranjay Mohan)
- Add kfuncs to traverse over wakeup_sources (Samuel Wu)
- Allow sleepable BPF programs to use LPM trie maps directly (Vlad
Poenaru)
- Many more fixes and cleanups across the verifier, BTF, sockmap,
devmap, bpffs, security hooks, s390/riscv/loongarch JITs,
rqspinlock, libbpf, bpftool, selftests"
* tag 'bpf-next-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (336 commits)
selftests/bpf: Work around llvm stack overflow in crypto progs
selftests/bpf: add test for bpf_msg_pop_data() overflow
bpf, sockmap: fix integer overflow in bpf_msg_pop_data() bounds check
sockmap: Fix use-after-free in udp_bpf_recvmsg()
bpf, sockmap: keep sk_msg copy state in sync
bpf, sockmap: Fix wrong rsge offset in bpf_msg_push_data()
bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data()
selftsets/bpf: Retry map update on helper_fill_hashmap()
selftests/bpf: Add test for sleepable lsm_cgroup rejection
selftests/bpf: Add test to verify the fix for bpf_setsockopt() helper
bpf: Fix bpf_get/setsockopt to tos for ipv4-mapped ipv6 socket
selftests/bpf: Avoid static LLVM linking for cross builds
selftests/bpf: Use common CFLAGS for urandom_read
selftests/bpf: Initialize operation name before use
tools/bpf: build: Append extra cflags
libbpf: Initialize CFLAGS before including Makefile.include
bpftool: Append extra host flags
bpftool: Avoid adding EXTRA_CFLAGS to HOST_CFLAGS
bpftool: Pass host flags to bootstrap libbpf
selftests/bpf: correct CONFIG_PPC64 macro name in comment
...
Pull simple_xattr updates from Christian Brauner:
"This reworks the simple xattr api to make it more efficient and easier
to use for all consumers.
The simple_xattr hash table moves from the inode into a per-superblock
cache, removing the per-inode overhead for the common case of few or
no xattrs. The interface now passes struct simple_xattrs ** so lazy
allocation is handled internally instead of by every caller, kernfs
xattr operations on kernfs nodes shared between multiple superblocks
are properly serialized, and tmpfs constructs "security.foo" xattr
names with kasprintf() instead of kmalloc() plus two memcpy()s.
A follow-up fix links kernfs nodes to their parent before the LSM init
hook runs: with the per-sb cache kernfs_xattr_set() computes the cache
via kernfs_root(kn), which faulted on a freshly allocated node when
selinux_kernfs_init_security() called into it - reproducible as a NULL
pointer dereference on the first cgroup mkdir on SELinux-enabled
systems.
On top of this bpffs gains support for trusted.* and security.* xattrs
so that user space and BPF LSM programs can attach metadata - for
example a content hash or a security label - to pinned objects and
directories and inspect it uniformly like on other filesystems. The
store is in-memory and non-persistent, living only for the lifetime of
the mount like everything else in bpffs"
* tag 'vfs-7.2-rc1.xattr' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
bpf: Add simple xattr support to bpffs
kernfs: link kn to its parent before the LSM init hook
simpe_xattr: use per-sb cache
simple_xattr: change interface to pass struct simple_xattrs **
tmpfs: simplify constructing "security.foo" xattr names
kernfs: fix xattr race condition with multiple superblocks
Map update and delete paths currently call bpf_obj_free_fields() when a
value is being replaced or recycled. That makes field destruction depend
on the context of the update/delete operation. For tracing programs this
can include NMI context, where referenced kptr destructors, uptr
unpinning, and graph root destruction are not generally safe.
Introduce bpf_obj_cancel_fields() for the reusable-value path. It only
performs NMI-safe cleanup for timer, workqueue, and task_work fields.
Fields that need full destruction are left attached to the recycled value
and are destroyed by the final cleanup path instead.
Switch array and hashtab update/delete/recycle paths to this cancel
helper. Keep bpf_obj_free_fields() for final map destruction and for
bpf_mem_alloc destructors. Preallocated hashtabs do not have allocator
destructors, so teardown continues to walk the normal and extra elements
and fully destroy their fields.
This deliberately relaxes the eager-free semantics of map update/delete
for special fields. Programs that relied on a recycled map slot becoming
empty immediately after update/delete were relying on behavior that
cannot be implemented safely from every BPF execution context without
offloading arbitrary destructors.
There is a chance this change breaks programs making assumptions
regarding the eager freeing of fields. If so, we can relax semantics to
cancellation only when irqs_disabled() is true in the future. However,
theoretically, map values that get reused eagerly already have weaker
guarantees as parallel users can recreate freed fields before the new
element becomes visible again.
Fixes: 14a324f6a6 ("bpf: Wire up freeing of referenced kptr")
Signed-off-by: Justin Suess <utilityemal77@gmail.com>
Co-developed-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260609202548.3571690-3-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf_obj_drop() runs bpf_obj_free_fields() synchronously for
program-allocated objects. When such an object contains NMI unsafe
fields, tracing programs that can run from arbitrary instrumented
context can reach that destruction from unsafe contexts, including NMI.
NMI is likely one instance of this problem, and other instances would
include possible unsafe reentrancy. Deferring bpf_obj_drop() is not
appealing either: it would add delayed-free machinery to a release
operation that otherwise has straightforward synchronous ownership
semantics.
Reject bpf_obj_drop() and bpf_percpu_obj_drop() from tracing programs
that may run from unsafe contexts unless every field in the object's BTF
record is explicitly NMI safe. Do not reject sleepable
BPF_PROG_TYPE_TRACING programs, since they are not the arbitrary/NMI
contexts that motivate the restriction.
Note that while bpf_rb_root and bpf_list_head would be NMI safe on their
own to free, the objects recursively held by them may not be; be
conservative and just mark them as not NMI safe for now.
Use a whitelist for the NMI-safe field set instead of listing only known
NMI unsafe fields. Locks, async fields, unreferenced kptrs, and
refcounts are known to be NMI safe because their destruction is either a
no-op, simple state reset, or async cancellation. Referenced kptrs,
percpu referenced kptrs, uptrs, graph roots, graph nodes, and any future
field type are rejected until audited for arbitrary tracing and NMI
contexts. This is less susceptible to future changes in fields that were
previously safe by exclusion, and to new fields being added without
updating this check.
Convert the existing recursive local-object drop success case to a
syscall program in the same commit, since this verifier change makes the
old tracing program form invalid. The test still exercises
bpf_obj_drop() releasing a referenced task kptr from a safe program
type.
Fixes: ac9f06050a ("bpf: Introduce bpf_obj_drop")
Signed-off-by: Justin Suess <utilityemal77@gmail.com>
Co-developed-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260609202548.3571690-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adding support to use session attachment with tracing_multi link.
Adding new BPF_TRACE_FSESSION_MULTI program attach type, that follows
the BPF_TRACE_FSESSION behaviour but on the tracing_multi link.
Such program is called on entry and exit of the attached function
and allows to pass cookie value from entry to exit execution.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-16-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add support to specify cookies for tracing_multi link.
Cookies are provided in array where each value is paired with provided
BTF ID value with the same array index.
Such cookie can be retrieved by bpf program with bpf_get_attach_cookie
helper call.
We need to sort cookies array together with ids array in check_dup_ids,
to keep the id->cookie relation.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-15-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adding bpf_trampoline_multi_attach/detach functions that allows to
attach/detach tracing program to multiple functions/trampolines.
The attachment is defined with bpf_program and array of BTF ids of
functions to attach the bpf program to.
Adding bpf_tracing_multi_link object that holds all the attached
trampolines and is initialized in attach and used in detach.
The attachment allocates or uses currently existing trampoline
for each function to attach and links it with the bpf program.
The attach works as follows:
- we get all the needed trampolines
- lock them and add the bpf program to each (__bpf_trampoline_link_prog)
- the trampoline_multi_ops passed in __bpf_trampoline_link_prog gathers
ftrace_hash (ip -> trampoline) objects
- we call update_ftrace_direct_add/mod to update needed locations
- we unlock all the trampolines
The detach works as follows:
- we lock all the needed trampolines
- remove the program from each (__bpf_trampoline_unlink_prog)
- the trampoline_multi_ops passed in __bpf_trampoline_unlink_prog gathers
ftrace_hash (ip -> trampoline) objects
- we call update_ftrace_direct_del/mod to update needed locations
- we unlock and put all the trampolines
We store the old image/flags in the trampoline before the update
and use it in case we need to rollback the attachment.
We keep the ftrace_hash objects allocated during attach in the link
so they can be used for detach as well.
Adding trampoline_(un)lock_all functions to (un)lock all trampolines
to gate the tracing_multi attachment.
Note this is supported only for archs (x86_64) with ftrace direct and
have single ops support.
CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS &&
CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS
It also needs CONFIG_BPF_SYSCALL enabled.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-13-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adding new program attach types multi tracing attachment:
BPF_TRACE_FENTRY_MULTI
BPF_TRACE_FEXIT_MULTI
and their base support in verifier code.
Programs with such attach type will use specific link attachment
interface coming in following changes.
This was suggested by Andrii some (long) time ago and turned out
to be easier than having special program flag for that.
Bpf programs with such types have 'bpf_multi_func' function set as
their attach_btf_id and keep module reference when it's specified
by attach_prog_fd.
They are also accepted as sleepable programs during verification,
and the real validation for specific BTF_IDs/functions will happen
during the multi link attachment in following changes.
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-11-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adding struct bpf_tramp_node to decouple the link out of the trampoline
attachment info.
At the moment the object for attaching bpf program to the trampoline is
'struct bpf_tramp_link':
struct bpf_tramp_link {
struct bpf_link link;
struct hlist_node tramp_hlist;
u64 cookie;
}
The link holds the bpf_prog pointer and forces one link - one program
binding logic. In following changes we want to attach program to multiple
trampolines but we want to keep just one bpf_link object.
Splitting struct bpf_tramp_link into:
struct bpf_tramp_link {
struct bpf_link link;
struct bpf_tramp_node node;
};
struct bpf_tramp_node {
struct bpf_link *link;
struct hlist_node tramp_hlist;
u64 cookie;
};
The 'struct bpf_tramp_link' defines standard single trampoline link
and 'struct bpf_tramp_node' is the attachment trampoline object with
pointer to the bpf_link object.
This will allow us to define link for multiple trampolines, like:
struct bpf_tracing_multi_link {
struct bpf_link link;
...
int nodes_cnt;
struct bpf_tracing_multi_node nodes[] __counted_by(nodes_cnt);
};
Cc: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-9-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adding mutex lock pool that replaces bpf trampolines mutex.
For tracing_multi link coming in following changes we need to lock all
the involved trampolines during the attachment. This could mean thousands
of mutex locks, which is not convenient.
As suggested by Andrii we can replace bpf trampolines mutex with mutex
pool, where each trampoline is hash-ed to one of the locks from the pool.
It's better to lock all the pool mutexes (32 at the moment) than
thousands of them.
There is 48 (MAX_LOCK_DEPTH) lock limit allowed to be simultaneously
held by task, so we need to keep 32 mutexes (5 bits) in the pool, so
when we lock them all in following changes the lockdep won't scream.
Removing the mutex_is_locked in bpf_trampoline_put, because we removed
the mutex from bpf_trampoline.
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-5-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add support for extended attributes on bpffs inodes so that user space
and BPF LSM programs can attach metadata, for example, a content hash
or a security label - to a pinned object or directory. BPF LSM or user
space tooling can then uniformly look at this (e.g. security.bpf.*) in
similar way to other fs'es. The store is in-memory and non-persistent:
it lives only for the lifetime of the mount, like everything else in
bpffs. The modelling is similar to tmpfs.
bpffs serves the trusted.* and security.* namespaces; user.* is left
unsupported. As bpffs is FS_USERNS_MOUNT, security.* is reachable by
the unprivileged mounter in a user namespace, and thus we are using
the simple_xattr_set_limited infra there (trusted.* needs global
CAP_SYS_ADMIN).
bpf_fill_super() is open-coded instead of using simple_fill_super(),
because the root inode must now be allocated through bpf_fs_alloc_inode()
i.e. carry the bpf_fs_inode wrapper and come from the right cache -
which requires s_op (and s_xattr) to be installed before the first
inode is created. While at it, also harden s_iflags with SB_I_NOEXEC
and SB_I_NODEV.
bpf_fs_listxattr() is only reachable through the filesystem via
i_op->listxattr, so the BPF token inode is left untouched. Name-based
fsetxattr()/fgetxattr() on a token fd still work since the get/set
handlers are installed at the superblock.
For security.* namespace, we use simple_xattr_set_limited() but
there was no simple_xattr_add_limited() API yet which was needed
in bpf_fs_initxattrs() to avoid underflows in the accounting. The
symlink target is freed in bpf_free_inode() rather than in
bpf_destroy_inode() so that it is released only after an RCU grace
period, as an RCU path walk following the symlink may still
dereference inode->i_link in security_inode_follow_link(). Lastly,
the bpf_symlink() allocated the symlink target is switched to
GFP_KERNEL_ACCOUNT, so the string is charged to the caller's memcg.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://patch.msgid.link/20260602074012.416289-1-daniel@iogearbox.net
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
BPF_PROG_LOAD verifies the loader signature but does not record the
outcome on the BPF program. [BPF] LSMs and audit can read attr->signature
and attr->keyring_id to infer "was this signed, and if so, against which
keyring".
Add prog->aux->sig (verdict + keyring_{type,serial}), populated by
bpf_prog_load before the LSM hook. keyring_type classifies the keyring
the load referenced (builtin, secondary, platform or user), while
keyring_serial records the serial of the keyring the signature was
actually validated against. System keyrings carry a pseudo key pointer
with no user-visible serial and are reported as 0, as are unsigned loads.
Failed verifications reject the load before the hook runs, so it observes
only either UNSIGNED or VERIFIED.
Signed-off-by: KP Singh <kpsingh@kernel.org>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260605213518.544262-1-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The loader verifies map->sha against the metadata hash in its
instructions. map->sha is calculated when BPF_OBJ_GET_INFO_BY_FD is
called on the frozen map.
While the map is frozen, the /signed loader/ must also ensure the map
is exclusive, as, without exclusivity (which a hostile host could just
omit when loading the loader), another BPF program with map access can
mutate the contents afterwards, so the check passes on stale data.
With the extra check as part of the signed loader, it now refuses to
move on with map->sha validation if the host set it up wrongly.
Fixes: fb2b0e2901 ("libbpf: Update light skeleton for signing")
Signed-off-by: KP Singh <kpsingh@kernel.org>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260601150248.394863-4-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf_map_get_info_by_fd() is the only caller of the ->map_get_hash
and always invokes it with hash_buf == map->sha and hash_buf_size
of SHA256_DIGEST_SIZE. array_map_get_hash() in turn lets sha256()
write the digest directly into that buffer (map->sha) and then
performs a trailing memcpy(), which evaluates to memcpy(map->sha,
map->sha, 32): a redundant self-copy. The hash_buf_size argument
was never used at all. Simplify this a bit, no functional change.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260601150248.394863-3-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Refactor object relationship tracking in the verifier and fix a dynptr
use-after-free bug where file/skb dynptrs are not invalidated when the
parent referenced object is freed.
Add parent_id to bpf_reg_state to precisely track child-parent
relationships. A child object's parent_id points to the parent object's
id. This replaces the PTR_TO_MEM-specific dynptr_id.
Remove ref_obj_id from bpf_reg_state by folding its role into the
existing id field. Previously, id tracked pointer identity for null
checking while ref_obj_id tracked the owning reference for lifetime
management. These are now unified: acquire helpers and kfuncs set id
to the acquired reference id, and release paths use id directly.
Add reg_is_referenced() which checks if a register is referenced by
looking up its id in the reference array. This replaces all former
ref_obj_id checks.
For release_reference(), invalidating an object now also invalidates
all descendants by traversing the object tree. This is done using
stack-based DFS to avoid recursive call chains of release_reference() ->
unmark_stack_slots_dynptr() -> release_reference(). Referenced objects
encountered during tree traversal are reported as leaked references.
Add parent_id to bpf_reference_state to enable hierarchical reference
tracking. When acquiring a reference, a parent_id can be specified to
link the new reference to an existing one (e.g., referenced dynptrs
acquire a reference with parent_id linking to the parent object's
reference).
Pointer casting:
For pointer casting helpers (bpf_sk_fullsock, bpf_tcp_sock), instead of
propagating ref_obj_id, the cast result reuses the same reference id as
the source pointer. Since the cast may return NULL for a non-NULL input,
the NULL case is explored as a separate verifier branch. This allows
releasing any of the original or cast pointers to invalidate all others.
Referenced dynptrs:
When constructing a referenced dynptr, acquire a intermediate reference
with parent_id linking to the parent referenced object. The dynptr and
all clones share the same parent_id (pointing to the intermediate ref)
but get unique ids for independent slice tracking. Releasing a
referenced dynptr releases the parent reference, which in turn
invalidates all clones and their derived slices.
Owning to non-owning reference conversion:
After converting owning to non-owning by clearing id (e.g.,
object(id=1) -> object(id=0)), the verifier releases the reference
state via release_reference_nomark().
Note that the error message "reference has not been acquired before" in
the helper and kfunc release paths is removed. This message was already
unreachable. The verifier only calls release_reference() after
confirming the reference is valid, so the condition could never trigger
in practice.
Fixes: 870c28588a ("bpf: net_sched: Add basic bpf qdisc kfuncs")
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-6-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tejun Heo says:
====================
This makes BPF arena memory directly dereferenceable from kernel code
(struct_ops callbacks, kfuncs). Each arena gets a per-arena scratch page
that an arch fault hook installs into empty PTEs on kernel-side faults,
after KFENCE. The faulting instruction retries and the violation is reported
through the program's BPF stream.
v4:
- Patch 1: note that the strict-zero cmpxchg is narrower than pte_none() in
inline comments on both x86 and arm64. (Andrea)
- Patch 2: stub bpf_arena_handle_page_fault() for !CONFIG_BPF_SYSCALL via a
new include/linux/bpf_defs.h. (lkp)
- Patch 7: scx_arena_alloc() retries via a loop instead of a single retry on
pool growth. (Andrea)
- Picked up Reviewed-by tags from Emil and Andrea.
v3: https://lore.kernel.org/r/20260520235052.4180316-1-tj@kernel.org
v2: https://lore.kernel.org/r/20260517211232.1670594-1-tj@kernel.org
v1 (RFC): https://lore.kernel.org/r/20260427105109.2554518-1-tj@kernel.org
Motivation
----------
sched_ext's ops_cid.set_cmask() hands the BPF scheduler a struct scx_cmask
*. The kernel translates a kernel cpumask to a cmask, but it had no way to
write into the arena, so the cmask lived in kernel memory and was passed as
a trusted pointer. BPF cmask helpers all operate on arena cmasks though, so
the BPF side had to word-by-word probe-read the kernel cmask into an arena
cmask via cmask_copy_from_kernel() before any helper could touch it. It
works, but is clumsy.
The shape isn't unique to set_cmask. Sub-scheduler support is on the way and
more sched_ext callbacks will want to pass structured data to BPF. Anywhere
a kfunc or struct_ops callback wants to hand a struct to a BPF program,
arena residence is the natural answer.
Approach
--------
Each arena gets a per-arena scratch page. Arenas stay sparsely mapped as
today - PTEs are populated only for allocated pages. A new arch fault hook
(bpf_arena_handle_page_fault) is wired into x86 page_fault_oops() and arm64
__do_kernel_fault(), after KFENCE. When a kernel-side access faults inside
an arena's kern_vm range, the helper walks the stack to find the BPF program
responsible, range-checks the fault address against prog->aux->arena, and
atomically installs the scratch page into the empty PTE via the new
ptep_try_set() wrapper. The kernel instruction retries and reads/writes the
scratch page. Free paths and map destruction treat scratch as non-owned.
Real allocation refuses to overwrite scratch (apply_range_set_cb returns
-EBUSY). A scratched address stays dead until map destroy, since its
presence means the BPF program has already malfunctioned.
The mechanism is default behavior - no UAPI flag.
What this preserves
-------------------
All the debugging properties of today's sparse-PTE design are preserved:
* BPF programs still fault on unmapped arena accesses. The fault semantics
(instruction retry with rdst = 0) and the violation report through
bpf_streams are unchanged for prog-side accesses.
* The first kernel-side touch of an unmapped address is reported via
bpf_streams the same way as a prog-side fault, with the stack walk
attributing it to the originating prog.
* User-side fault on a never-scratched address still lazy-allocates a real
page (or returns SIGSEGV under BPF_F_SEGV_ON_FAULT). User-side fault on a
scratched address SIGSEGVs.
What changes for the kernel-side caller is just that an unmapped deref no
longer oopses - it retries through the scratch page and emits a violation
report. The same shape today's BPF instruction faults have.
Patches 1-2 (atomic PTE install + arena scratch-page recovery)
--------------------------------------------------------------
mm: Add ptep_try_set() for lockless empty-slot installs
bpf: Recover arena kernel faults with scratch page
Patches 3-5 (helpers used by struct_ops registration)
-----------------------------------------------------
bpf: Add sleepable variant of bpf_arena_alloc_pages for kernel callers
bpf: Add bpf_struct_ops_for_each_prog()
bpf/arena: Add bpf_arena_map_kern_vm_start() and bpf_prog_arena()
====================
Link: https://lore.kernel.org/bpf/20260522172219.1423324-1-tj@kernel.org/
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
struct bpf_arena is opaque to callers outside arena.c. Add two helpers
for struct_ops subsystems that need to reach into an arena:
bpf_arena_map_kern_vm_start(struct bpf_map *map)
returns @map's kern_vm_start. A sched_ext follow-up needs this
to translate kern_va <-> uaddr.
bpf_prog_arena(struct bpf_prog *prog)
returns the bpf_map of the arena referenced by @prog (NULL if
@prog references no arena). The verifier enforces at most one
arena per program. Used by struct_ops callers that auto-discover
an arena from a member prog and need to take a map reference.
Suggested-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260522172219.1423324-6-tj@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add a helper that walks the member progs of the struct_ops map
containing a given @kdata vmtable. struct_ops ->reg() callbacks (and
similar) sometimes need to inspect the loaded BPF programs, e.g. to
discover maps they reference via prog->aux->used_maps.
The implementation mirrors bpf_struct_ops_id(): container_of @kdata
to recover the bpf_struct_ops_map, then iterate st_map->links[i]->prog
for i in [0, funcs_cnt). Same access pattern, no new locking - by the
time ->reg() fires st_map is fully populated and stable.
A sched_ext follow-up walks the member progs of a cid-form scheduler's
struct_ops map, reads prog->aux->arena directly, and requires all member
progs to reference exactly one arena, without requiring the BPF program
to call a registration kfunc.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260522172219.1423324-5-tj@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The existing kernel-side export of bpf_arena_alloc_pages is _non_sleepable
only - it's used by the verifier to inline the kfunc when the call site is
non-sleepable. There is no sleepable equivalent for kernel callers. The
kfunc bpf_arena_alloc_pages itself is BPF-only.
sched_ext needs sleepable kernel-side allocs for its arena pool init/grow
paths. Add bpf_arena_alloc_pages_sleepable() mirroring the _non_sleepable
wrapper but passing sleepable=true to arena_alloc_pages().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260522172219.1423324-4-tj@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
BPF arena usage is becoming more prevalent, but kernel <-> BPF communication
over arena memory is awkward today. Data has to be staged through a trusted
kernel pointer with extra code and copying on the BPF side. While reads
through arena pointers can use a fault-safe helper, writes don't have a good
solution. The in-line alternative would need instruction emulation or asm
fixup labels.
Enable direct kernel-side reads and writes within GUARD_SZ / 2 of any
handed-in arena pointer, without bounds checking. A per-arena scratch page
is installed by the arch fault path into empty arena kernel PTEs - x86 from
page_fault_oops() for not-present faults, arm64 from __do_kernel_fault() for
translation faults, both after the existing exception-table and KFENCE
handling. The faulting instruction retries and the access is also reported
through the program's BPF stream, preserving error reporting.
bpf_prog_find_from_stack() resolves the current BPF program (and its arena)
from the kernel stack - no new bpf_run_ctx state is added. Recovery covers
the 4 GiB arena plus the upper half-guard (GUARD_SZ / 2). The lower
half-guard is excluded because well-behaved kfuncs only access forward from
arena pointers. The kfunc-author contract - access at most GUARD_SZ / 2 past
a handed-in pointer - is documented in Documentation/bpf/kfuncs.rst.
The install is lock-free via ptep_try_set(). On race-loss the winning
installer's PTE is already valid, so the access retry succeeds. The arena
clear path uses ptep_get_and_clear() so installer and clearer race through
atomic accessors. No flush_tlb_kernel_range() afterwards. Stale "not mapped"
entries just cause one extra re-fault, cheaper than a global IPI on every
install.
Scratch exists only to keep the kernel from oopsing on an in-line arena
access. Its presence at a PTE means the BPF program has already
malfunctioned, and the violation is reported through the program's BPF
stream. The only requirement for behavior on a scratched PTE is that the
kernel doesn't crash. In particular, any user-side access through such a PTE
may segfault. The shared scratch page is freed once during map destruction.
BPF instruction faults continue to use the existing JIT exception-table
path. This patch changes only the kernel-text fault path. No UAPI flag is
added. The new behavior is the default.
v2: Use ptep_get_and_clear() in apply_range_clear_cb(). (David)
v3: Stub bpf_arena_handle_page_fault() for !CONFIG_BPF_SYSCALL. (lkp)
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Cc: David Hildenbrand <david@kernel.org>
Link: https://lore.kernel.org/r/20260522172219.1423324-3-tj@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When a main program with exception_boundary has outgoing stack
arguments (e.g. from calling subprogs with >5 args), bpf_throw() fails
to correctly restore callee-saved registers, causing a kernel crash.
The x86 JIT allocates the outgoing stack arg area below the
callee-saved registers via 'sub rsp, outgoing_rsp' in the prologue.
When bpf_throw() unwinds, it captures the main program's sp (which
includes this outgoing area) and passes it to the exception callback.
The callback gets rsp and rbp, followed by pop_callee_regs, but rsp
points into the outgoing arg area rather than the callee-saved
registers, so the pops restore garbage values. Returning to the
kernel with corrupted callee-saved registers causes a crash.
Fix this by adjusting the sp (adding stack_arg_sp_adjust) passed to
the exception callback, so it points to the bottom of the callee-saved
registers instead of the outgoing arg area. When stack_arg_sp_adjust
is 0 (the common case), this is a no-op.
Fixes: 324c3ca6ee ("bpf,x86: Implement JIT support for stack arguments")
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260517150702.288031-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add x86_64 JIT support for BPF functions and kfuncs with more than
5 arguments. The extra arguments are passed through a stack area
addressed by register r11 (BPF_REG_PARAMS) in BPF bytecode,
which the JIT translates to native code.
The JIT follows the x86-64 calling convention for both BPF-to-BPF
and kfunc calls:
- Arg 6 is passed in the R9 register
- Args 7+ are passed on the stack
Incoming arg 6 (BPF r11+8) is translated to a MOV from R9 rather
than a memory load. Incoming args 7+ (BPF r11+16, r11+24, ...) map
directly to [rbp + 16], [rbp + 24], ..., matching the x86-64 stack
layout after CALL + PUSH RBP, so no offset adjustment is needed.
tail_call_reachable is rejected by the verifier and priv_stack is
disabled by the JIT when stack args exist, so R9 is always
available. When BPF bytecode writes to the arg-6 stack slot
(offset -8), the JIT emits a MOV into R9 instead of a memory store.
Outgoing args 7+ are placed at [rsp] in a pre-allocated area below
callee-saved registers, using:
native_off = outgoing_arg_base - outgoing_rsp - bpf_off - 16
The native x86_64 stack layout with stack arguments:
high address
+-------------------------+
| incoming stack arg N | [rbp + 16 + (N-7)*8] (from caller)
| ... |
| incoming stack arg 7 | [rbp + 16]
+-------------------------+
| return address | [rbp + 8]
| saved rbp | [rbp]
+-------------------------+
| BPF program stack | (round_up(stack_depth, 8) bytes)
+-------------------------+
| callee-saved regs | (r12, rbx, r13, r14, r15 as needed)
+-------------------------+
| outgoing arg M | [rsp + (M-7)*8]
| ... |
| outgoing arg 7 | [rsp]
+-------------------------+ rsp
low address
Acked-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260513045122.2393118-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The next commit will add support for reporting logs via extended common
attributes, including 'log_true_size'.
To prepare for that, refactor the 'log_true_size' reporting logic by
introducing a new struct bpf_log_attr to encapsulate log-related behavior:
* bpf_log_attr_init(): initialize log fields, which will support
extended common attributes in the next commit.
* bpf_log_attr_finalize(): handle log finalization and write back
'log_true_size' to userspace.
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260512153157.28382-4-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Currently, the BPF instruction set allows bpf-to-bpf calls (or internal
calls, pseudo calls) to use a 32-bit imm field to represent the relative
jump offset.
However, when JIT is disabled or falls back to the interpreter, the
verifier invokes bpf_patch_call_args() to rewrite the call instruction.
In this function, the 32-bit imm is downcast to s16 and stored in the off
field.
void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth)
{
stack_depth = max_t(u32, stack_depth, 1);
insn->off = (s16) insn->imm;
insn->imm = interpreters_args[(round_up(stack_depth, 32) / 32) - 1] -
__bpf_call_base_args;
insn->code = BPF_JMP | BPF_CALL_ARGS;
}
If the original imm exceeds the s16 range (i.e., a jump offset greater
than 32767 instructions), this downcast silently truncates the offset,
resulting in an incorrect call target.
Fix this by:
1. In bpf_patch_call_args(), keeping the imm field unchanged and using the
off field to store the index of the interpreter function.
2. In ___bpf_prog_run() for the JMP_CALL_ARGS case, retrieving the
interpreter function pointer from the interpreters_args array using the
off field as the index, and passing the original imm to calculate the
last argument of the interpreter function.
After these changes, the truncation issue is resolved, and __bpf_call_base_args
is also no longer needed and can be removed, which makes the code cleaner.
Performance: In ___bpf_prog_run() for the JMP_CALL_ARGS case, changing the
retrieval of the interpreter function pointer from pointer addition to
direct array indexing improves performance. The possible reason is that the
latter has better instruction-level parallelism. See the v5 discussion [1]
for more details.
[1] https://lore.kernel.org/bpf/f120c3c4-6999-414a-b514-518bb64b4758@zju.edu.cn/
To avoid requiring bpftool changes, keep the new imm/off encoding internal
and restore the legacy xlated dump layout in bpf_insn_prepare_dump().
For bpf-to-bpf call offsets that do not fit in s16, export off as 0 instead
of a truncated and misleading value.
Fixes: 1ea47e01ad ("bpf: add support for bpf_call to interpreter")
Fixes: 7105e828c0 ("bpf: allow for correlation of maps and helpers in dump")
Suggested-by: Xu Kuohai <xukuohai@huaweicloud.com>
Suggested-by: Puranjay Mohan <puranjay@kernel.org>
Co-developed-by: Tianci Cao <ziye@zju.edu.cn>
Signed-off-by: Tianci Cao <ziye@zju.edu.cn>
Co-developed-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Yazhou Tang <tangyazhou518@outlook.com>
Link: https://lore.kernel.org/r/20260506094714.419842-3-tangyazhou@zju.edu.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The interpreters_args array only accommodates stack depths up to
MAX_BPF_STACK (512 bytes). However, do_misc_fixups() may allow a larger
stack depth if JIT is requested.
If JIT compilation later fails and falls back to the interpreter, the
verifier invokes bpf_patch_call_args() with this oversized stack depth.
This causes a load-time out-of-bounds (OOB) read when calculating the
interpreter function pointer index.
Fix this by changing bpf_patch_call_args() to return an int and explicitly
rejecting the JIT fallback (returning -EINVAL) if the stack depth exceeds
MAX_BPF_STACK.
Fixes: 1ea47e01ad ("bpf: add support for bpf_call to interpreter")
Co-developed-by: Tianci Cao <ziye@zju.edu.cn>
Signed-off-by: Tianci Cao <ziye@zju.edu.cn>
Co-developed-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Yazhou Tang <tangyazhou518@outlook.com>
Acked-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/20260506094714.419842-2-tangyazhou@zju.edu.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Currently, MAX_BPF_FUNC_ARGS is used for tracepoint related progs where
the number of parameters cannot exceed MAX_BPF_FUNC_ARGS.
Here, MAX_BPF_FUNC_ARGS is reused to set a limit of the number of arguments
for bpf functions and kfuncs. The current value for MAX_BPF_FUNC_ARGS
is 12 which should be sufficient for majority of bpf functions and
kfuncs.
Acked-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260423033511.2542870-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add bpf_prog_run_array_sleepable() for running BPF program arrays
on faultable tracepoints. Unlike bpf_prog_run_array_uprobe(), it
includes per-program recursion checking for private stack safety
and hardcodes is_uprobe to false.
Skip dummy_bpf_prog at the top of the loop. When
bpf_prog_array_delete_safe() replaces a detached program with
dummy_bpf_prog on allocation failure, the dummy is statically
allocated and has NULL active, stats, and aux fields. Identify
it by prog->len == 0, since every real program has at least one
instruction.
Keep bpf_prog_run_array_uprobe() unchanged for uprobe callers.
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/20260422-sleepable_tracepoints-v13-2-99005dff21ef@meta.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
A BPF TCP congestion control program can call bpf_setsockopt() from
its callbacks. In current kernels, if it calls
bpf_setsockopt(TCP_NODELAY) from cwnd_event_tx_start(), the call can
re-enter the TCP transmit path before the outer tcp_transmit_skb()
has completed and advanced the send head.
This can re-trigger CA_EVENT_TX_START and lead to unbounded recursion:
tcp_transmit_skb()
-> tcp_event_data_sent()
-> tcp_ca_event(sk, CA_EVENT_TX_START)
-> cwnd_event_tx_start()
-> bpf_setsockopt(TCP_NODELAY)
-> tcp_push_pending_frames()
-> tcp_write_xmit()
-> tcp_transmit_skb()
This leads to unbounded recursion and can overflow the kernel stack.
Reject TCP_NODELAY with -EOPNOTSUPP for bpf-tcp-cc by introducing
a dedicated setsockopt proto for BPF_PROG_TYPE_STRUCT_OPS TCP
congestion control programs. To keep it simple, all tcp-cc ops is
rejected for TCP_NODELAY.
Fixes: 7e41df5dbb ("bpf: Add a few optnames to bpf_setsockopt")
Suggested-by: Martin KaFai Lau <martin.lau@linux.dev>
Signed-off-by: KaFai Wan <kafai.wan@linux.dev>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://patch.msgid.link/20260421155804.135786-3-kafai.wan@linux.dev
Redefine dynptr mutability and fix inconsistency in the verifier and
kfunc signatures. Dynptr mutability is at two levels. The first is
the bpf_dynptr structure and the second is the memory the dynptr points
to. The verifer currently tracks the mutability of the bpf_dynptr struct
through helper and kfunc prototypes, where "const struct bpf_dynptr *"
means the structure itself is immutable. The second level is tracked
in upper bit of bpf_dynptr->size in runtime and is not changed in this
patch.
There are two type of inconsistency in the verfier regarding the
mutability of the bpf_dynptr struct. First, there are many existing
kfuncs whose prototypes are wrong. For example, bpf_dynptr_adjust()
mutates a dynptr's start and offset but marks the argument as a const
pointer. At the same time many other kfuncs that does not mutate the
dynptr but mark themselves as mutable. Second, the verifier currently
does not honor the const qualifier in kfunc prototypes as it determines
whether tagging the arg_type with MEM_RDONLY or not based on the register
state.
Since all the verifier care is to prevent CONST_PTR_TO_DYNPTR from
being destroyed in callback and global subprogram, redefine the
mutability at the bpf_dynptr level to just bpf_dynptr_kern->data. Then,
explicitly prohibit passing CONST_PTR_TO_DYNPTR to an argument tagged
with MEM_UNINIT or OBJ_RELEASE. The mutability of a dynptr's view is not
really interesting so drop MEM_RDONLY annotation for dynptr from the
helpers and kfuncs. Plus, if the mutability of the entire bpf_dynptr
were to be done correctly, it would kill the bpf_dynptr_adjust() usage
in callback and global subporgram.
Implementation wise
- First, make sure all kfunc arg are correctly tagged: Tag the dynptr
argument of bpf_dynptr_file_discard() with OBJ_RELEASE.
- Then, in process_dynptr_func(), make sure CONST_PTR_TO_DYNPTR cannot
be passed to argument tagged with MEM_UNINIT or OBJ_RELEASE. For
MEM_UNINIT, it is already checked by is_dynptr_reg_valid_uninit().
For OBJ_RELEASE, check against OBJ_RELEASE instead of MEM_RDONLY and
drop a now identical check in unmark_stack_slots_dynptr().
- Remove the mutual exclusive check between MEM_UNINIT and MEM_RDONLY,
but don't add a MEM_UNINIT and OBJ_RELEASE version as it is obviously
wrong.
Note that while this patch stops following the C semantic for the
mutability of bpf_dynptr, the prototype of kfuncs are still fixed to
maintain the correct C semantics in the implementation. Adding or
removing the const qualifier does not break backward compatibility.
In addition, fix kfuncs dropping the const qualifier when casting the
opaque bpf_dynptr to bpf_dynptr_kern.
In test_kfunc_dynptr_param.c, initialize dynptr to 0 to avoid
-Wuninitialized-const-pointer warning.
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/20260414191014.1218567-1-ameryhung@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Introduce helper bpf_insn_is_indirect_target to check whether a BPF
instruction is an indirect jump target.
Since the verifier knows which instructions are indirect jump targets,
add a new flag indirect_target to struct bpf_insn_aux_data to mark
them. The verifier sets this flag when verifying an indirect jump target
instruction, and the helper checks the flag to determine whether an
instruction is an indirect jump target.
Reviewed-by: Anton Protopopov <a.s.protopopov@gmail.com> #v8
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> #v12
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/20260416064341.151802-4-xukuohai@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Apparently, struct bpf_empty_prog_array exists entirely to populate a
single element of "items" in a global variable. "null_prog" is only
used during the initializer.
None of this is needed; globals will be correctly sized with an array
initializer of a flexible-array member.
So, remove struct bpf_empty_prog_array and adjust the rest of the code,
accordingly.
With these changes, fix the following warnings:
./include/linux/bpf.h:2369:31: warning: structure containing a flexible
array member is not at the end of another structure [-Wflex-array-member-not-at-end]
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/acr7Whmn0br3xeBP@kspp
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Recently, tracepoints were switched from using disabled preemption
(which acts as RCU read section) to SRCU-fast when they are not
faultable. This means that to do a proper grace period wait for programs
running in such tracepoints, we must use SRCU's grace period wait.
This is only for non-faultable tracepoints, faultable ones continue
using RCU Tasks Trace.
However, bpf_link_free() currently does call_rcu() for all cases when
the link is non-sleepable (hence, for tracepoints, non-faultable). Fix
this by doing a call_srcu() grace period wait.
As far RCU Tasks Trace gp -> RCU gp chaining is concerned, it is deemed
unnecessary for tracepoint programs. The link and program are either
accessed under RCU Tasks Trace protection, or SRCU-fast protection now.
The earlier logic of chaining both RCU Tasks Trace and RCU gp waits was
to generalize the logic, even if it conceded an extra RCU gp wait,
however that is unnecessary for tracepoints even before this change.
In practice no cost was paid since rcu_trace_implies_rcu_gp() was always
true. Hence we need not chaining any RCU gp after the SRCU gp.
For instance, in the non-faultable raw tracepoint, the RCU read section
of the program in __bpf_trace_run() is enclosed in the SRCU gp, likewise
for faultable raw tracepoint, the program is under the RCU Tasks Trace
protection. Hence, the outermost scope can be waited upon to ensure
correctness.
Also, sleepable programs cannot be attached to non-faultable
tracepoints, so whenever program or link is sleepable, only RCU Tasks
Trace protection is being used for the link and prog.
Fixes: a46023d561 ("tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast")
Reviewed-by: Sun Jian <sun.jian.kdev@gmail.com>
Reviewed-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20260331211021.1632902-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
BPF hash map may now use the map_check_btf() callback to decide whether
to set a dtor on its bpf_mem_alloc or not. Unlike C++ where members can
opt out of const-ness using mutable, we must lose the const qualifier on
the callback such that we can avoid the ugly cast. Make the change and
adjust all existing users, and lose the comment in hashtab.c.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260227224806.646888-3-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
Allowing sleepable programs to use tail calls.
Making sure we can't mix sleepable and non-sleepable bpf programs
in tail call map (BPF_MAP_TYPE_PROG_ARRAY) and allowing it to be
used in sleepable programs.
Sleepable programs can be preempted and sleep which might bring
new source of race conditions, but both direct and indirect tail
calls should not be affected.
Direct tail calls work by patching direct jump to callee into bpf
caller program, so no problem there. We atomically switch from nop
to jump instruction.
Indirect tail call reads the callee from the map and then jumps to
it. The callee bpf program can't disappear (be released) from the
caller, because it is executed under rcu lock (rcu_read_lock_trace).
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260130081208.1130204-2-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit fixes a security issue where BPF_PROG_DETACH on tcx or
netkit devices could be executed by any user when no program fd was
provided, bypassing permission checks. The fix adds a capability
check for CAP_NET_ADMIN or CAP_SYS_ADMIN in this case.
Fixes: e420bed025 ("bpf: Add fd-based tcx multi-prog infra with link support")
Signed-off-by: Guillaume Gonnet <ggonnet.linux@gmail.com>
Link: https://lore.kernel.org/r/20260127160200.10395-1-ggonnet.linux@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Implement session cookie for fsession. The session cookies will be stored
in the stack, and the layout of the stack will look like this:
return value -> 8 bytes
argN -> 8 bytes
...
arg1 -> 8 bytes
nr_args -> 8 bytes
ip (optional) -> 8 bytes
cookie2 -> 8 bytes
cookie1 -> 8 bytes
The offset of the cookie for the current bpf program, which is in 8-byte
units, is stored in the
"(((u64 *)ctx)[-1] >> BPF_TRAMP_COOKIE_INDEX_SHIFT) & 0xFF". Therefore, we
can get the session cookie with ((u64 *)ctx)[-offset].
Implement and inline the bpf_session_cookie() for the fsession in the
verifier.
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Link: https://lore.kernel.org/r/20260124062008.8657-6-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
If fsession exists, we will use the bit (1 << BPF_TRAMP_IS_RETURN_SHIFT)
in ((u64 *)ctx)[-1] to store the "is_return" flag.
The logic of bpf_session_is_return() for fsession is implemented in the
verifier by inline following code:
bool bpf_session_is_return(void *ctx)
{
return (((u64 *)ctx)[-1] >> BPF_TRAMP_IS_RETURN_SHIFT) & 1;
}
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Co-developed-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260124062008.8657-5-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Introduce BPF_F_ALL_CPUS flag support for percpu_cgroup_storage maps to
allow updating values for all CPUs with a single value for update_elem
API.
Introduce BPF_F_CPU flag support for percpu_cgroup_storage maps to
allow:
* update value for specified CPU for update_elem API.
* lookup value for specified CPU for lookup_elem API.
The BPF_F_CPU flag is passed via map_flags along with embedded cpu info.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260107022022.12843-6-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Introduce BPF_F_ALL_CPUS flag support for percpu_hash and lru_percpu_hash
maps to allow updating values for all CPUs with a single value for both
update_elem and update_batch APIs.
Introduce BPF_F_CPU flag support for percpu_hash and lru_percpu_hash
maps to allow:
* update value for specified CPU for both update_elem and update_batch
APIs.
* lookup value for specified CPU for both lookup_elem and lookup_batch
APIs.
The BPF_F_CPU flag is passed via:
* map_flags along with embedded cpu info.
* elem_flags along with embedded cpu info.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260107022022.12843-4-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Introduce support for the BPF_F_ALL_CPUS flag in percpu_array maps to
allow updating values for all CPUs with a single value for both
update_elem and update_batch APIs.
Introduce support for the BPF_F_CPU flag in percpu_array maps to allow:
* update value for specified CPU for both update_elem and update_batch
APIs.
* lookup value for specified CPU for both lookup_elem and lookup_batch
APIs.
The BPF_F_CPU flag is passed via:
* map_flags of lookup_elem and update_elem APIs along with embedded cpu
info.
* elem_flags of lookup_batch and update_batch APIs along with embedded
cpu info.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260107022022.12843-3-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linus Torvalds
Justin Suess
Jiri Olsa
Daniel Borkmann
KP Singh
Amery Hung
Alexei Starovoitov
Tejun Heo
Kumar Kartikeya Dwivedi
Yonghong Song
Leon Hwang
Yazhou Tang
Mykyta Yatsenko
KaFai Wan
Xu Kuohai
Gustavo A. R. Silva
Kees Cook
Guillaume Gonnet
Menglong Dong