4.14-stable review patch. If anyone has any objections, please let me know.
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From: Miles Chen miles.chen@mediatek.com
[ Upstream commit 11066386efa692f77171484c32ea30f6e5a0d729 ]
When slub_debug=O is set. It is possible to clear debug flags for an "unmergeable" slab cache in kmem_cache_open(). It makes the "unmergeable" cache became "mergeable" in sysfs_slab_add().
These caches will generate their "unique IDs" by create_unique_id(), but it is possible to create identical unique IDs. In my experiment, sgpool-128, names_cache, biovec-256 generate the same ID ":Ft-0004096" and the kernel reports "sysfs: cannot create duplicate filename '/kernel/slab/:Ft-0004096'".
To repeat my experiment, set disable_higher_order_debug=1, CONFIG_SLUB_DEBUG_ON=y in kernel-4.14.
Fix this issue by setting unmergeable=1 if slub_debug=O and the the default slub_debug contains any no-merge flags.
call path: kmem_cache_create() __kmem_cache_alias() -> we set SLAB_NEVER_MERGE flags here create_cache() __kmem_cache_create() kmem_cache_open() -> clear DEBUG_METADATA_FLAGS sysfs_slab_add() -> the slab cache is mergeable now
sysfs: cannot create duplicate filename '/kernel/slab/:Ft-0004096' ------------[ cut here ]------------ WARNING: CPU: 0 PID: 1 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x60/0x7c Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 4.14.0-rc7ajb-00131-gd4c2e9f-dirty #123 Hardware name: linux,dummy-virt (DT) task: ffffffc07d4e0080 task.stack: ffffff8008008000 PC is at sysfs_warn_dup+0x60/0x7c LR is at sysfs_warn_dup+0x60/0x7c pc : lr : pstate: 60000145 Call trace: sysfs_warn_dup+0x60/0x7c sysfs_create_dir_ns+0x98/0xa0 kobject_add_internal+0xa0/0x294 kobject_init_and_add+0x90/0xb4 sysfs_slab_add+0x90/0x200 __kmem_cache_create+0x26c/0x438 kmem_cache_create+0x164/0x1f4 sg_pool_init+0x60/0x100 do_one_initcall+0x38/0x12c kernel_init_freeable+0x138/0x1d4 kernel_init+0x10/0xfc ret_from_fork+0x10/0x18
Link: http://lkml.kernel.org/r/1510365805-5155-1-git-send-email-miles.chen@mediate... Signed-off-by: Miles Chen miles.chen@mediatek.com Acked-by: Christoph Lameter cl@linux.com Cc: Pekka Enberg penberg@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/slub.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/mm/slub.c +++ b/mm/slub.c @@ -5704,6 +5704,10 @@ static int sysfs_slab_add(struct kmem_ca return 0; }
+ if (!unmergeable && disable_higher_order_debug && + (slub_debug & DEBUG_METADATA_FLAGS)) + unmergeable = 1; + if (unmergeable) { /* * Slabcache can never be merged so we can use the name proper.