[PATCH v2] mm/slub: Add check for s->flags in the alloc_tagging_slab_free_hook
From: Hao Ge
Date: Thu Aug 15 2024 - 21:34:13 EST
From: Hao Ge <gehao@xxxxxxxxxx>
When enable CONFIG_MEMCG & CONFIG_KFENCE & CONFIG_KMEMLEAK,
the following warning always occurs,This is because the
following call stack occurred:
mem_pool_alloc
kmem_cache_alloc_noprof
slab_alloc_node
kfence_alloc
Once the kfence allocation is successful,slab->obj_exts will not be empty,
because it has already been assigned a value in kfence_init_pool.
Since in the prepare_slab_obj_exts_hook function,we perform a check for
s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE),the alloc_tag_add function
will not be called as a result.Therefore,ref->ct remains NULL.
However,when we call mem_pool_free,since obj_ext is not empty,
it eventually leads to the alloc_tag_sub scenario being invoked.
This is where the warning occurs.
So we should add corresponding checks in the alloc_tagging_slab_free_hook.
For __GFP_NO_OBJ_EXT case,I didn't see the specific case where it's
using kfence,so I won't add the corresponding check in
alloc_tagging_slab_free_hook for now.
[ 3.734349] ------------[ cut here ]------------
[ 3.734807] alloc_tag was not set
[ 3.735129] WARNING: CPU: 4 PID: 40 at ./include/linux/alloc_tag.h:130 kmem_cache_free+0x444/0x574
[ 3.735866] Modules linked in: autofs4
[ 3.736211] CPU: 4 UID: 0 PID: 40 Comm: ksoftirqd/4 Tainted: G W 6.11.0-rc3-dirty #1
[ 3.736969] Tainted: [W]=WARN
[ 3.737258] Hardware name: QEMU KVM Virtual Machine, BIOS unknown 2/2/2022
[ 3.737875] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 3.738501] pc : kmem_cache_free+0x444/0x574
[ 3.738951] lr : kmem_cache_free+0x444/0x574
[ 3.739361] sp : ffff80008357bb60
[ 3.739693] x29: ffff80008357bb70 x28: 0000000000000000 x27: 0000000000000000
[ 3.740338] x26: ffff80008207f000 x25: ffff000b2eb2fd60 x24: ffff0000c0005700
[ 3.740982] x23: ffff8000804229e4 x22: ffff800082080000 x21: ffff800081756000
[ 3.741630] x20: fffffd7ff8253360 x19: 00000000000000a8 x18: ffffffffffffffff
[ 3.742274] x17: ffff800ab327f000 x16: ffff800083398000 x15: ffff800081756df0
[ 3.742919] x14: 0000000000000000 x13: 205d344320202020 x12: 5b5d373038343337
[ 3.743560] x11: ffff80008357b650 x10: 000000000000005d x9 : 00000000ffffffd0
[ 3.744231] x8 : 7f7f7f7f7f7f7f7f x7 : ffff80008237bad0 x6 : c0000000ffff7fff
[ 3.744907] x5 : ffff80008237ba78 x4 : ffff8000820bbad0 x3 : 0000000000000001
[ 3.745580] x2 : 68d66547c09f7800 x1 : 68d66547c09f7800 x0 : 0000000000000000
[ 3.746255] Call trace:
[ 3.746530] kmem_cache_free+0x444/0x574
[ 3.746931] mem_pool_free+0x44/0xf4
[ 3.747306] free_object_rcu+0xc8/0xdc
[ 3.747693] rcu_do_batch+0x234/0x8a4
[ 3.748075] rcu_core+0x230/0x3e4
[ 3.748424] rcu_core_si+0x14/0x1c
[ 3.748780] handle_softirqs+0x134/0x378
[ 3.749189] run_ksoftirqd+0x70/0x9c
[ 3.749560] smpboot_thread_fn+0x148/0x22c
[ 3.749978] kthread+0x10c/0x118
[ 3.750323] ret_from_fork+0x10/0x20
[ 3.750696] ---[ end trace 0000000000000000 ]---
Fixes: 4b8736964640 ("mm/slab: add allocation accounting into slab allocation and free paths")
Signed-off-by: Hao Ge <gehao@xxxxxxxxxx>
---
mm/slub.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/mm/slub.c b/mm/slub.c
index c9d8a2497fd6..a77f354f8325 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2116,6 +2116,10 @@ alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
if (!mem_alloc_profiling_enabled())
return;
+ /* slab->obj_exts might not be NULL if it was created for MEMCG accounting. */
+ if (s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE))
+ return;
+
obj_exts = slab_obj_exts(slab);
if (!obj_exts)
return;
--
2.25.1