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kfence: zero guard page after out-of-bounds access 

After an out-of-bounds accesses, zero the guard page before re-protecting
in kfence_guarded_free().  On one hand this helps make the failure mode of
subsequent out-of-bounds accesses more deterministic, but could also
prevent certain information leaks.

Link: https://lkml.kernel.org/r/20210312121653.348518-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Marco Elver 2021-05-04 18:40:18 -07:00 committed by Linus Torvalds
parent 0c4ff27a0e
commit 94868a1e12
1 changed files with 1 additions and 0 deletions
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mm/kfence/core.c
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@ -372,6 +372,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z
/* Restore page protection if there was an OOB access. */
if (meta->unprotected_page) {
memzero_explicit((void *)ALIGN_DOWN(meta->unprotected_page, PAGE_SIZE), PAGE_SIZE);
kfence_protect(meta->unprotected_page);
meta->unprotected_page = 0;
}