mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-09-22 09:34:56 +02:00
Alexei Starovoitov
aa89592fcb
Jiri Olsa says:
====================
bpf: Disable preemption in perf_event_output helpers code
hi,
we got report of kernel crash [1][3] within bpf_event_output helper.
The reason is the nesting protection code in bpf_event_output that expects
disabled preemption, which is not guaranteed for programs executed by
bpf_prog_run_array_cg.
I managed to reproduce on tracing side where we have the same problem
in bpf_perf_event_output. The reproducer [2] just creates busy uprobe
and call bpf_perf_event_output helper a lot.
v3 changes:
- added acks and fixed 'Fixes' tag style [Hou Tao]
- added Closes tag to patch 2
v2 changes:
- I changed 'Fixes' commits to where I saw we switched from preempt_disable
to migrate_disable, but I'm not completely sure about the patch 2, because
it was tricky to find, would be nice if somebody could check on that
thanks,
jirka
[1] https://github.com/cilium/cilium/issues/26756
[2] https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/commit/?h=bpf_output_fix_reproducer&id=8054dcc634121b884c7c331329d61d93351d03b5
[3] slack:
[66194.378161] BUG: kernel NULL pointer dereference, address: 0000000000000001
[66194.378324] #PF: supervisor instruction fetch in kernel mode
[66194.378447] #PF: error_code(0x0010) - not-present page
...
[66194.378692] Oops: 0010 [#1] PREEMPT SMP NOPTI
...
[66194.380666] <TASK>
[66194.380775] ? perf_output_sample+0x12a/0x9a0
[66194.380902] ? finish_task_switch.isra.0+0x81/0x280
[66194.381024] ? perf_event_output+0x66/0xa0
[66194.381148] ? bpf_event_output+0x13a/0x190
[66194.381270] ? bpf_event_output_data+0x22/0x40
[66194.381391] ? bpf_prog_dfc84bbde731b257_cil_sock4_connect+0x40a/0xacb
[66194.381519] ? xa_load+0x87/0xe0
[66194.381635] ? __cgroup_bpf_run_filter_sock_addr+0xc1/0x1a0
[66194.381759] ? release_sock+0x3e/0x90
[66194.381876] ? sk_setsockopt+0x1a1/0x12f0
[66194.381996] ? udp_pre_connect+0x36/0x50
[66194.382114] ? inet_dgram_connect+0x93/0xa0
[66194.382233] ? __sys_connect+0xb4/0xe0
[66194.382353] ? udp_setsockopt+0x27/0x40
[66194.382470] ? __pfx_udp_push_pending_frames+0x10/0x10
[66194.382593] ? __sys_setsockopt+0xdf/0x1a0
[66194.382713] ? __x64_sys_connect+0xf/0x20
[66194.382832] ? do_syscall_64+0x3a/0x90
[66194.382949] ? entry_SYSCALL_64_after_hwframe+0x72/0xdc
[66194.383077] </TASK>
---
====================
Link: https://lore.kernel.org/r/20230725084206.580930-1-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.