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authorAndrey Konovalov <andreyknvl@google.com>2019-02-20 22:19:32 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-02-21 09:01:00 -0800
commitd36a63a943e37081e92e4abdf4a207fd2e83a006 (patch)
tree148469fb82f7151fc255e9b449e0ef4629b574ca /mm/slub.c
parent18e506610238eda2b0c5a19a123d3d6ec0ab2de6 (diff)
downloadlinux-d36a63a943e37081e92e4abdf4a207fd2e83a006.tar.bz2
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.c13
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