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kasan, mm: optimize krealloc poisoning 

Currently, krealloc() always calls ksize(), which unpoisons the whole
object including the redzone.  This is inefficient, as kasan_krealloc()
repoisons the redzone for objects that fit into the same buffer.

This patch changes krealloc() instrumentation to use uninstrumented
__ksize() that doesn't unpoison the memory.  Instead, kasan_kreallos() is
changed to unpoison the memory excluding the redzone.

For objects that don't fit into the old allocation, this patch disables
KASAN accessibility checks when copying memory into a new object instead
of unpoisoning it.

Link: https://lkml.kernel.org/r/9bef90327c9cb109d736c40115684fd32f49e6b0.1612546384.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2021-02-25 17:20:23 -08:00 committed by Linus Torvalds
parent 26a5ca7a73
commit d12d9ad816
2 changed files with 24 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
mm/kasan/common.c
View File

@ -476,7 +476,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
/*
* The object has already been unpoisoned by kasan_slab_alloc() for
* kmalloc() or by ksize() for krealloc().
* kmalloc() or by kasan_krealloc() for krealloc().
*/
/*
@ -526,7 +526,7 @@ void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
/*
* The object has already been unpoisoned by kasan_alloc_pages() for
* alloc_pages() or by ksize() for krealloc().
* alloc_pages() or by kasan_krealloc() for krealloc().
*/
/*
@ -554,8 +554,16 @@ void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flag
if (unlikely(object == ZERO_SIZE_PTR))
return (void *)object;
/*
* Unpoison the object's data.
* Part of it might already have been unpoisoned, but it's unknown
* how big that part is.
*/
kasan_unpoison(object, size);
page = virt_to_head_page(object);
/* Piggy-back on kmalloc() instrumentation to poison the redzone. */
if (unlikely(!PageSlab(page)))
return __kasan_kmalloc_large(object, size, flags);
else

20
mm/slab_common.c
View File

@ -1136,19 +1136,27 @@ static __always_inline void *__do_krealloc(const void *p, size_t new_size,
void *ret;
size_t ks;
if (likely(!ZERO_OR_NULL_PTR(p)) && !kasan_check_byte(p))
return NULL;
ks = ksize(p);
/* Don't use instrumented ksize to allow precise KASAN poisoning. */
if (likely(!ZERO_OR_NULL_PTR(p))) {
if (!kasan_check_byte(p))
return NULL;
ks = kfence_ksize(p) ?: __ksize(p);
} else
ks = 0;
/* If the object still fits, repoison it precisely. */
if (ks >= new_size) {
p = kasan_krealloc((void *)p, new_size, flags);
return (void *)p;
}
ret = kmalloc_track_caller(new_size, flags);
if (ret && p)
memcpy(ret, p, ks);
if (ret && p) {
/* Disable KASAN checks as the object's redzone is accessed. */
kasan_disable_current();
memcpy(ret, kasan_reset_tag(p), ks);
kasan_enable_current();
}
return ret;
}