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linux/mm/kfence
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Alexander Potapenko d155aab90f mm/kfence: fix KASAN hardware tag faults during late enablement 
When KASAN hardware tags are enabled, re-enabling KFENCE late (via
/sys/module/kfence/parameters/sample_interval) causes KASAN faults.

This happens because the KFENCE pool and metadata are allocated via the
page allocator, which tags the memory, while KFENCE continues to access it
using untagged pointers during initialization.

Use __GFP_SKIP_KASAN for late KFENCE pool and metadata allocations to
ensure the memory remains untagged, consistent with early allocations from
memblock.  To support this, add __GFP_SKIP_KASAN to the allowlist in
__alloc_contig_verify_gfp_mask().

Link: https://lkml.kernel.org/r/20260220144940.2779209-1-glider@google.com
Fixes: 0ce20dd840 ("mm: add Kernel Electric-Fence infrastructure")
Signed-off-by: Alexander Potapenko <glider@google.com>
Suggested-by: Ernesto Martinez Garcia <ernesto.martinezgarcia@tugraz.at>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Marco Elver <elver@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-02-24 11:13:27 -08:00
..
.kunitconfig kfence: test: use new suite_{init/exit} support, add .kunitconfig 2022-05-02 12:35:57 -06:00
core.c mm/kfence: fix KASAN hardware tag faults during late enablement 2026-02-24 11:13:27 -08:00
kfence.h kfence: Enable context analysis 2026-01-05 16:43:34 +01:00
kfence_test.c mm: fix benign off-by-one bugs 2026-01-20 19:44:19 -08:00
Makefile kfence: Enable context analysis 2026-01-05 16:43:34 +01:00
report.c kfence: Enable context analysis 2026-01-05 16:43:34 +01:00