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Syzbot reports a KASAN failure early during boot on arm64 when building with GCC 12.2.0 and using the Software Tag-Based KASAN mode: | BUG: KASAN: invalid-access in smp_build_mpidr_hash arch/arm64/kernel/setup.c:133 [inline] | BUG: KASAN: invalid-access in setup_arch+0x984/0xd60 arch/arm64/kernel/setup.c:356 | Write of size 4 at addr 03ff800086867e00 by task swapper/0 | Pointer tag: [03], memory tag: [fe] Initial triage indicates that the report is a false positive and a thorough investigation of the crash by Mark Rutland revealed the root cause to be a bug in GCC: > When GCC is passed `-fsanitize=hwaddress` or > `-fsanitize=kernel-hwaddress` it ignores > `__attribute__((no_sanitize_address))`, and instruments functions > we require are not instrumented. > > [...] > > All versions [of GCC] I tried were broken, from 11.3.0 to 14.2.0 > inclusive. > > I think we have to disable KASAN_SW_TAGS with GCC until this is > fixed Disable Software Tag-Based KASAN when building with GCC by making CC_HAS_KASAN_SW_TAGS depend on !CC_IS_GCC. Cc: Andrey Konovalov <andreyknvl@gmail.com> Suggested-by: Mark Rutland <mark.rutland@arm.com> Reported-by: syzbot+908886656a02769af987@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/000000000000f362e80620e27859@google.com Link: https://lore.kernel.org/r/ZvFGwKfoC4yVjN_X@J2N7QTR9R3 Link: https://bugzilla.kernel.org/show_bug.cgi?id=218854 Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Acked-by: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/r/20241014161100.18034-1-will@kernel.org Signed-off-by: Will Deacon <will@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 reStructuredText 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.