kasan: fix unit tests with CONFIG_UBSAN_LOCAL_BOUNDS enabled
These tests deliberately access these arrays out of bounds, which will cause the dynamic local bounds checks inserted by CONFIG_UBSAN_LOCAL_BOUNDS to fail and panic the kernel. To avoid this problem, access the arrays via volatile pointers, which will prevent the compiler from being able to determine the array bounds. These accesses use volatile pointers to char (char *volatile) rather than the more conventional pointers to volatile char (volatile char *) because we want to prevent the compiler from making inferences about the pointer itself (i.e. its array bounds), not the data that it refers to. Link: https://lkml.kernel.org/r/20210507025915.1464056-1-pcc@google.com Link: https://linux-review.googlesource.com/id/I90b1713fbfa1bf68ff895aef099ea77b98a7c3b9Signed-off-by: Peter Collingbourne <pcc@google.com> Tested-by: Alexander Potapenko <glider@google.com> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Peter Collingbourne <pcc@google.com> Cc: George Popescu <georgepope@android.com> Cc: Elena Petrova <lenaptr@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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