4.9-stable review patch. If anyone has any objections, please let me know.
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From: Dmitry Vyukov dvyukov@google.com
commit 61448479a9f2c954cde0cfe778cb6bec5d0a748d upstream.
Slub does not call kmalloc_slab() for sizes > KMALLOC_MAX_CACHE_SIZE, instead it falls back to kmalloc_large().
For slab KMALLOC_MAX_CACHE_SIZE == KMALLOC_MAX_SIZE and it calls kmalloc_slab() for all allocations relying on NULL return value for over-sized allocations.
This inconsistency leads to unwanted warnings from kmalloc_slab() for over-sized allocations for slab. Returning NULL for failed allocations is the expected behavior.
Make slub and slab code consistent by checking size > KMALLOC_MAX_CACHE_SIZE in slab before calling kmalloc_slab().
While we are here also fix the check in kmalloc_slab(). We should check against KMALLOC_MAX_CACHE_SIZE rather than KMALLOC_MAX_SIZE. It all kinda worked because for slab the constants are the same, and slub always checks the size against KMALLOC_MAX_CACHE_SIZE before kmalloc_slab(). But if we get there with size > KMALLOC_MAX_CACHE_SIZE anyhow bad things will happen. For example, in case of a newly introduced bug in slub code.
Also move the check in kmalloc_slab() from function entry to the size > 192 case. This partially compensates for the additional check in slab code and makes slub code a bit faster (at least theoretically).
Also drop __GFP_NOWARN in the warning check. This warning means a bug in slab code itself, user-passed flags have nothing to do with it.
Nothing of this affects slob.
Link: http://lkml.kernel.org/r/20180927171502.226522-1-dvyukov@gmail.com Signed-off-by: Dmitry Vyukov dvyukov@google.com Reported-by: syzbot+87829a10073277282ad1@syzkaller.appspotmail.com Reported-by: syzbot+ef4e8fc3a06e9019bb40@syzkaller.appspotmail.com Reported-by: syzbot+6e438f4036df52cbb863@syzkaller.appspotmail.com Reported-by: syzbot+8574471d8734457d98aa@syzkaller.appspotmail.com Reported-by: syzbot+af1504df0807a083dbd9@syzkaller.appspotmail.com Acked-by: Christoph Lameter cl@linux.com Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Pekka Enberg penberg@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/slab.c | 4 ++++ mm/slab_common.c | 12 ++++++------ 2 files changed, 10 insertions(+), 6 deletions(-)
--- a/mm/slab.c +++ b/mm/slab.c @@ -3690,6 +3690,8 @@ __do_kmalloc_node(size_t size, gfp_t fla struct kmem_cache *cachep; void *ret;
+ if (unlikely(size > KMALLOC_MAX_CACHE_SIZE)) + return NULL; cachep = kmalloc_slab(size, flags); if (unlikely(ZERO_OR_NULL_PTR(cachep))) return cachep; @@ -3725,6 +3727,8 @@ static __always_inline void *__do_kmallo struct kmem_cache *cachep; void *ret;
+ if (unlikely(size > KMALLOC_MAX_CACHE_SIZE)) + return NULL; cachep = kmalloc_slab(size, flags); if (unlikely(ZERO_OR_NULL_PTR(cachep))) return cachep; --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -883,18 +883,18 @@ struct kmem_cache *kmalloc_slab(size_t s { int index;
- if (unlikely(size > KMALLOC_MAX_SIZE)) { - WARN_ON_ONCE(!(flags & __GFP_NOWARN)); - return NULL; - } - if (size <= 192) { if (!size) return ZERO_SIZE_PTR;
index = size_index[size_index_elem(size)]; - } else + } else { + if (unlikely(size > KMALLOC_MAX_CACHE_SIZE)) { + WARN_ON(1); + return NULL; + } index = fls(size - 1); + }
#ifdef CONFIG_ZONE_DMA if (unlikely((flags & GFP_DMA)))