kasan: Disable Software Tag-Based KASAN with GCC

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>

0 files changed, 0 insertions, 0 deletions