[PATCH 4.14 028/100] mm: dont warn about large allocations for slab

From: Greg Kroah-Hartman
Date: Thu Nov 29 2018 - 09:25:16 EST

4.14-stable review patch. If anyone has any objections, please let me know.


From: Dmitry Vyukov <dvyukov@xxxxxxxxxx>

commit 61448479a9f2c954cde0cfe778cb6bec5d0a748d upstream.

Slub does not call kmalloc_slab() for sizes > KMALLOC_MAX_CACHE_SIZE,
instead it falls back to kmalloc_large().

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@xxxxxxxxx
Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Reported-by: syzbot+87829a10073277282ad1@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+ef4e8fc3a06e9019bb40@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+6e438f4036df52cbb863@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+8574471d8734457d98aa@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+af1504df0807a083dbd9@xxxxxxxxxxxxxxxxxxxxxxxxx
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

mm/slab.c | 4 ++++
mm/slab_common.c | 12 ++++++------
2 files changed, 10 insertions(+), 6 deletions(-)

--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3670,6 +3670,8 @@ __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;
@@ -3705,6 +3707,8 @@ 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
@@ -971,18 +971,18 @@ 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)

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);
+ }

if (unlikely((flags & GFP_DMA)))