bio: Fix potential memory leak in bio_find_or_create_slab()

Do not leak memory by updating pointer with potentially NULL realloc return value.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: NAlexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

fs/bio.c

@@ -73,7 +73,7 @@ static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
 {
 	unsigned int sz = sizeof(struct bio) + extra_size;
 	struct kmem_cache *slab = NULL;
-	struct bio_slab *bslab;
+	struct bio_slab *bslab, *new_bio_slabs;
 	unsigned int i, entry = -1;
 
 	mutex_lock(&bio_slab_lock);
@@ -97,11 +97,12 @@ static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
 
 	if (bio_slab_nr == bio_slab_max && entry == -1) {
 		bio_slab_max <<= 1;
-		bio_slabs = krealloc(bio_slabs,
-				     bio_slab_max * sizeof(struct bio_slab),
-				     GFP_KERNEL);
-		if (!bio_slabs)
+		new_bio_slabs = krealloc(bio_slabs,
+					 bio_slab_max * sizeof(struct bio_slab),
+					 GFP_KERNEL);
+		if (!new_bio_slabs)
 			goto out_unlock;
+		bio_slabs = new_bio_slabs;
 	}
 	if (entry == -1)
 		entry = bio_slab_nr++;