From: Suren Baghdasaryan Date: Mon, 15 Sep 2025 20:09:17 +0000 (-0700) Subject: slab: prevent warnings when slab obj_exts vector allocation fails X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4038016397da5c1cebb10e7c85a36d06123724a8;p=thirdparty%2Fkernel%2Fstable.git slab: prevent warnings when slab obj_exts vector allocation fails When object extension vector allocation fails, we set slab->obj_exts to OBJEXTS_ALLOC_FAIL to indicate the failure. Later, once the vector is successfully allocated, we will use this flag to mark codetag references stored in that vector as empty to avoid codetag warnings. slab_obj_exts() used to retrieve the slab->obj_exts vector pointer checks slab->obj_exts for being either NULL or a pointer with MEMCG_DATA_OBJEXTS bit set. However it does not handle the case when slab->obj_exts equals OBJEXTS_ALLOC_FAIL. Add the missing condition to avoid extra warning. Fixes: 09c46563ff6d ("codetag: debug: introduce OBJEXTS_ALLOC_FAIL to mark failed slab_ext allocations") Reported-by: Shakeel Butt Closes: https://lore.kernel.org/all/jftidhymri2af5u3xtcqry3cfu6aqzte3uzlznhlaylgrdztsi@5vpjnzpsemf5/ Signed-off-by: Suren Baghdasaryan Cc: stable@vger.kernel.org # v6.10+ Acked-by: Shakeel Butt Signed-off-by: Vlastimil Babka --- diff --git a/mm/slab.h b/mm/slab.h index 248b34c839b7c..0dd3f33c09634 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -526,8 +526,12 @@ static inline struct slabobj_ext *slab_obj_exts(struct slab *slab) unsigned long obj_exts = READ_ONCE(slab->obj_exts); #ifdef CONFIG_MEMCG - VM_BUG_ON_PAGE(obj_exts && !(obj_exts & MEMCG_DATA_OBJEXTS), - slab_page(slab)); + /* + * obj_exts should be either NULL, a valid pointer with + * MEMCG_DATA_OBJEXTS bit set or be equal to OBJEXTS_ALLOC_FAIL. + */ + VM_BUG_ON_PAGE(obj_exts && !(obj_exts & MEMCG_DATA_OBJEXTS) && + obj_exts != OBJEXTS_ALLOC_FAIL, slab_page(slab)); VM_BUG_ON_PAGE(obj_exts & MEMCG_DATA_KMEM, slab_page(slab)); #endif return (struct slabobj_ext *)(obj_exts & ~OBJEXTS_FLAGS_MASK);