From 1dba91a0493b7ffe9cbbcf7a8df1b361ddcac515 Mon Sep 17 00:00:00 2001 From: "Harry Yoo (Oracle)" Date: Mon, 13 Jul 2026 23:28:49 +0900 Subject: [PATCH] mm/slab: fix a memory leak due to bootstrapping sheaves twice 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. Fixes: 913ffd3a1bf5 ("slab: handle kmalloc sheaves bootstrap") Cc: stable@vger.kernel.org Signed-off-by: Harry Yoo (Oracle) Reviewed-by: Suren Baghdasaryan Link: https://patch.msgid.link/20260713-kmalloc-no-objext-v3-1-47c7bd138de7@kernel.org Signed-off-by: Vlastimil Babka (SUSE) --- 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); } } }