[PATCH slab/for-next-fixes v2 1/3] mm/slab: fix a memory leak due to bootstrapping sheaves twice

["Harry Yoo (Oracle)" <harry@kernel.org>]

When kmalloc caches are aliased, multiple cache pointers reference
the same kmem_cache. As a result, iterating over kmalloc indices and
bootstrapping sheaves can bootstrap the same cache more than once and
leak memory.

Currently, this could happen when the architecture specifies
minimum alignment for slab caches that is larger than
ARCH_KMALLOC_MINALIGN.

Bootstrap sheaves only when the cache does not have them already.
Add a warning when bootstrap_cache_sheaves() is called for a cache
that already has sheaves enabled.

Cc: stable@vger.kernel.org
Fixes: 913ffd3a1bf5 ("slab: handle kmalloc sheaves bootstrap")
Signed-off-by: Harry Yoo (Oracle) <harry@kernel.org>
---
 mm/slub.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 65febe957886..f9461a0c47d3 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -8497,6 +8497,8 @@ static void __init bootstrap_cache_sheaves(struct kmem_cache *s)
 	bool failed = false;
 	int node, cpu;
 
+	VM_WARN_ON_ONCE(cache_has_sheaves(s));
+
 	capacity = calculate_sheaf_capacity(s, &empty_args);
 
 	/* capacity can be 0 due to debugging or SLUB_TINY */
@@ -8548,8 +8550,11 @@ static void __init bootstrap_kmalloc_sheaves(void)
 
 	for (type = KMALLOC_NORMAL; type <= KMALLOC_PARTITION_END; type++) {
 		for (int idx = 0; idx < KMALLOC_SHIFT_HIGH + 1; idx++) {
-			if (kmalloc_caches[type][idx])
-				bootstrap_cache_sheaves(kmalloc_caches[type][idx]);
+			struct kmem_cache *s = kmalloc_caches[type][idx];
+
+			/* Do not bootstrap twice when caches are aliased */
+			if (s && !cache_has_sheaves(s))
+				bootstrap_cache_sheaves(s);
 		}
 	}
 }

-- 
2.53.0