| Message ID | 20180927171502.226522-1-dvyukov@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] mm: don't warn about large allocations for slab | expand |
On 9/27/18 7:15 PM, Dmitry Vyukov wrote: > From: Dmitry Vyukov <dvyukov@google.com> > > 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. > > Signed-off-by: Dmitry Vyukov <dvyukov@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: Andrew Morton <akpm@linux-foundation.org> > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > 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: Vlastimil Babka <vbabka@suse.cz>
diff --git a/mm/slab.c b/mm/slab.c index 9515798f37b2d..2a5654bb3b3ff 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3675,6 +3675,8 @@ __do_kmalloc_node(size_t size, gfp_t flags, int node, unsigned long caller) 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; @@ -3710,6 +3712,8 @@ static __always_inline void *__do_kmalloc(size_t size, gfp_t flags, 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; diff --git a/mm/slab_common.c b/mm/slab_common.c index 1f903589980f9..7eb8dc136c1cb 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1023,18 +1023,18 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags) { unsigned 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); + } return kmalloc_caches[kmalloc_type(flags)][index]; }