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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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Lorenzo Stoakes (ARM)
76df4edf7d
[ Upstream commit27c32e5538] Previous commits have established the invariant that kernel page table freeing is performed while an mmap read lock on init_mm is held, which fixes races between ptdump and kernel page table freeing over init_mm. However, x86 and arm64 can perform a ptdump over an mm other than init_mm via ptdump_walk_pgd() and since kernel memory ranges are shared across non-kernel mm's, this means that the race still exists for these cases. Fix this by acquiring a nested mmap write lock for init_mm in ptdump_walk_pgd(). This is safe as we take this after mmap write locking the mm, and nothing acquires the init_mm lock first before locking an arbitrary mm, so no deadlock is possible. Also update walk_page_range_debug() to assert that init_mm is write locked, add a comment explaining why and remove some redundant code, and eliminate the unnecessary and confusing invocation of walk_kernel_page_table_range(). We can safely remove the non-NULL check for walk.mm, as the mmap lock asserts would NULL pointer deref if it was (and of course no callers do this). The first point at which ptdump can race kernel page table freeing is commitb6bdb7517c("mm/vmalloc: add interfaces to free unmapped page table"), so we target this in the Fixes tag. Link: https://lore.kernel.org/20260723-series-vmap-race-fix-v6-4-8cc77dcc0018@kernel.org Fixes:b6bdb7517c("mm/vmalloc: add interfaces to free unmapped page table") Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Reviewed-by: Kiryl Shutsemau <kas@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: "Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com> Cc: "Borislav Petkov (AMD)" <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Carlier <devnexen@gmail.com> Cc: Dev Jain <dev.jain@arm.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Liam R. Howlett <liam@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Shakeel Butt <shakeel.butt@linux.dev> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Toshi Kani <toshi.kani@hpe.com> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vlastimil Babka <vbabka@kernel.org> Cc: Will Deacon <will@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.