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| author | Andrey Konovalov <andreyknvl@google.com> | 2019-02-20 22:19:32 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-02-21 09:01:00 -0800 |
| commit | d36a63a943e37081e92e4abdf4a207fd2e83a006 (patch) | |
| tree | 148469fb82f7151fc255e9b449e0ef4629b574ca /mm/slub.c | |
| parent | 18e506610238eda2b0c5a19a123d3d6ec0ab2de6 (diff) | |
| download | lwn-d36a63a943e37081e92e4abdf4a207fd2e83a006.tar.gz lwn-d36a63a943e37081e92e4abdf4a207fd2e83a006.zip | |
kasan, slub: fix more conflicts with CONFIG_SLAB_FREELIST_HARDENED
When CONFIG_KASAN_SW_TAGS is enabled, ptr_addr might be tagged. Normally,
this doesn't cause any issues, as both set_freepointer() and
get_freepointer() are called with a pointer with the same tag. However,
there are some issues with CONFIG_SLUB_DEBUG code. For example, when
__free_slub() iterates over objects in a cache, it passes untagged
pointers to check_object(). check_object() in turns calls
get_freepointer() with an untagged pointer, which causes the freepointer
to be restored incorrectly.
Add kasan_reset_tag to freelist_ptr(). Also add a detailed comment.
Link: http://lkml.kernel.org/r/bf858f26ef32eb7bd24c665755b3aee4bc58d0e4.1550103861.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reported-by: Qian Cai <cai@lca.pw>
Tested-by: Qian Cai <cai@lca.pw>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
| -rw-r--r-- | mm/slub.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/mm/slub.c b/mm/slub.c index 80da3a40b74d..c80e6699357c 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -249,7 +249,18 @@ static inline void *freelist_ptr(const struct kmem_cache *s, void *ptr, unsigned long ptr_addr) { #ifdef CONFIG_SLAB_FREELIST_HARDENED - return (void *)((unsigned long)ptr ^ s->random ^ ptr_addr); + /* + * When CONFIG_KASAN_SW_TAGS is enabled, ptr_addr might be tagged. + * Normally, this doesn't cause any issues, as both set_freepointer() + * and get_freepointer() are called with a pointer with the same tag. + * However, there are some issues with CONFIG_SLUB_DEBUG code. For + * example, when __free_slub() iterates over objects in a cache, it + * passes untagged pointers to check_object(). check_object() in turns + * calls get_freepointer() with an untagged pointer, which causes the + * freepointer to be restored incorrectly. + */ + return (void *)((unsigned long)ptr ^ s->random ^ + (unsigned long)kasan_reset_tag((void *)ptr_addr)); #else return ptr; #endif |