[PATCH 4.9 16/92] mm: dont warn about large allocations for slab

[Greg Kroah-Hartman]

4.9-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().

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@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
@@ -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)))