mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

mm, slub: restore the original intention of prefetch_freepointer() 

commit 0882ff9190 upstream.

In SLUB, prefetch_freepointer() is used when allocating an object from
cache's freelist, to make sure the next object in the list is cache-hot,
since it's probable it will be allocated soon.

Commit 2482ddec67 ("mm: add SLUB free list pointer obfuscation") has
unintentionally changed the prefetch in a way where the prefetch is
turned to a real fetch, and only the next->next pointer is prefetched.
In case there is not a stream of allocations that would benefit from
prefetching, the extra real fetch might add a useless cache miss to the
allocation.  Restore the previous behavior.

Link: http://lkml.kernel.org/r/20180809085245.22448-1-vbabka@suse.cz
Fixes: 2482ddec67 ("mm: add SLUB free list pointer obfuscation")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Vlastimil Babka 2020-04-26 09:06:17 +02:00 committed by Greg Kroah-Hartman
parent bf2b525b18
commit 69e4bfba09
1 changed files with 1 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
mm/slub.c
View File

@ -269,8 +269,7 @@ static inline void *get_freepointer(struct kmem_cache *s, void *object)
static void prefetch_freepointer(const struct kmem_cache *s, void *object)
{
if (object)
prefetch(freelist_dereference(s, object + s->offset));
prefetch(object + s->offset);
}
static inline void *get_freepointer_safe(struct kmem_cache *s, void *object)