kasan: fix kasan_byte_accessible() to be consistent with actual checks
We can sometimes end up with kasan_byte_accessible() being called on non-slab memory. For example ksize() and krealloc() may end up calling it on KFENCE allocated memory. In this case the memory will be tagged with KASAN_SHADOW_INIT, which a subsequent patch ("kasan: initialize shadow to TAG_INVALID for SW_TAGS") will set to the same value as KASAN_TAG_INVALID, causing kasan_byte_accessible() to fail when called on non-slab memory. This highlighted the fact that the check in kasan_byte_accessible() was inconsistent with checks as implemented for loads and stores (kasan_check_range() in SW tags mode and hardware-implemented checks in HW tags mode). kasan_check_range() does not have a check for KASAN_TAG_INVALID, and instead has a comparison against KASAN_SHADOW_START. In HW tags mode, we do not have either, but we do set TCR_EL1.TCMA which corresponds with the comparison against KASAN_TAG_KERNEL. Therefore, update kasan_byte_accessible() for both SW and HW tags modes to correspond with the respective checks on loads and stores. Link: https://linux-review.googlesource.com/id/Ic6d40803c57dcc6331bd97fbb9a60b0d38a65a36 Link: https://lkml.kernel.org/r/20210405220647.1965262-1-pcc@google.com Signed-off-by:Peter Collingbourne <pcc@google.com> Reviewed-by:
Andrey Konovalov <andreyknvl@gmail.com> Reviewed-by:
Marco Elver <elver@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Peter Collingbourne <pcc@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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f76e0c41
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