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| author | Will Deacon <will@kernel.org> | 2024-10-14 18:11:00 +0200 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2024-10-15 12:38:10 +0200 |
| commit | 7aed6a2c51ffc97a126e0ea0c270fab7af97ae18 (patch) | |
| tree | e593e046b858ea69e0bee3a8ce09d91f56636b94 | |
| parent | Documentation/protection-keys: add AArch64 to documentation (diff) | |
| download | linux-7aed6a2c51ffc97a126e0ea0c270fab7af97ae18.tar.xz linux-7aed6a2c51ffc97a126e0ea0c270fab7af97ae18.zip | |
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>
| -rw-r--r-- | lib/Kconfig.kasan | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index 98016e137b7f..233ab2096924 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -22,8 +22,11 @@ config ARCH_DISABLE_KASAN_INLINE config CC_HAS_KASAN_GENERIC def_bool $(cc-option, -fsanitize=kernel-address) +# GCC appears to ignore no_sanitize_address when -fsanitize=kernel-hwaddress +# is passed. See https://bugzilla.kernel.org/show_bug.cgi?id=218854 (and +# the linked LKML thread) for more details. config CC_HAS_KASAN_SW_TAGS - def_bool $(cc-option, -fsanitize=kernel-hwaddress) + def_bool !CC_IS_GCC && $(cc-option, -fsanitize=kernel-hwaddress) # This option is only required for software KASAN modes. # Old GCC versions do not have proper support for no_sanitize_address. @@ -98,7 +101,7 @@ config KASAN_SW_TAGS help Enables Software Tag-Based KASAN. - Requires GCC 11+ or Clang. + Requires Clang. Supported only on arm64 CPUs and relies on Top Byte Ignore. |