iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

mm/slub: fix a slab missed to be freed problem

Browse Source 
When enable kasan and kfence's in-kernel kunit test with slub_debug on,
it caught a problem (in linux-next tree):

 ------------[ cut here ]------------
 kmem_cache_destroy test: Slab cache still has objects when called from test_exit+0x1a/0x30
 WARNING: CPU: 3 PID: 240 at mm/slab_common.c:492 kmem_cache_destroy+0x16c/0x170
 Modules linked in:
 CPU: 3 PID: 240 Comm: kunit_try_catch Tainted: G    B            N 6.0.0-rc7-next-20220929 #52
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
 RIP: 0010:kmem_cache_destroy+0x16c/0x170
 Code: 41 5c 41 5d e9 a5 04 0b 00 c3 cc cc cc cc 48 8b 55 60 48 8b 4c 24 20 48 c7 c6 40 37 d2 82 48 c7 c7 e8 a0 33 83 e8 4e d7 14 01 <0f> 0b eb a7 41 56 41 89 d6 41 55 49 89 f5 41 54 49 89 fc 55 48 89
 RSP: 0000:ffff88800775fea0 EFLAGS: 00010282
 RAX: 0000000000000000 RBX: ffffffff83bdec48 RCX: 0000000000000000
 RDX: 0000000000000001 RSI: 1ffff11000eebf9e RDI: ffffed1000eebfc6
 RBP: ffff88804362fa00 R08: ffffffff81182e58 R09: ffff88800775fbdf
 R10: ffffed1000eebf7b R11: 0000000000000001 R12: 000000008c800d00
 R13: ffff888005e78040 R14: 0000000000000000 R15: ffff888005cdfad0
 FS:  0000000000000000(0000) GS:ffff88807ed00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 000000000360e001 CR4: 0000000000370ee0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  <TASK>
  test_exit+0x1a/0x30
  kunit_try_run_case+0xad/0xc0
  kunit_generic_run_threadfn_adapter+0x26/0x50
  kthread+0x17b/0x1b0

It was biscted to commit c7323a5ad0 ("mm/slub: restrict sysfs
validation to debug caches and make it safe")

The problem is inside free_debug_processing(), under certain
circumstances the slab can be removed from the partial list but not
freed by discard_slab() and thus n->nr_slabs is not decreased
accordingly. During shutdown, this non-zero n->nr_slabs is detected and
reported.

Specifically, the problem is that there are two checks for detecting a
full partial list by comparing n->nr_partial >= s->min_partial where the
latter check is affected by remove_partial() decreasing n->nr_partial
between the checks. Reoganize the code so there is a single check
upfront.

Link: https://lore.kernel.org/all/20220930100730.250248-1-feng.tang@intel.com/
Fixes: c7323a5ad0 ("mm/slub: restrict sysfs validation to debug caches and make it safe")
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Feng Tang 2022-09-30 18:07:30 +08:00 committed by Vlastimil Babka
parent 1f04b07d97
commit b731e3575f
1 changed files with 14 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
mm/slub.c
View File

@ -2836,22 +2836,25 @@ out:
set_freepointer(s, tail, prior);
slab->freelist = head;
/* Do we need to remove the slab from full or partial list? */
/*
* If the slab is empty, and node's partial list is full,
* it should be discarded anyway no matter it's on full or
* partial list.
*/
if (slab->inuse == 0 && n->nr_partial >= s->min_partial)
slab_free = slab;
if (!prior) {
/* was on full list */
remove_full(s, n, slab);
} else if (slab->inuse == 0 &&
n->nr_partial >= s->min_partial) {
if (!slab_free) {
add_partial(n, slab, DEACTIVATE_TO_TAIL);
stat(s, FREE_ADD_PARTIAL);
}
} else if (slab_free) {
remove_partial(n, slab);
stat(s, FREE_REMOVE_PARTIAL);
}
/* Do we need to discard the slab or add to partial list? */
if (slab->inuse == 0 && n->nr_partial >= s->min_partial) {
slab_free = slab;
} else if (!prior) {
add_partial(n, slab, DEACTIVATE_TO_TAIL);
stat(s, FREE_ADD_PARTIAL);
}
}
if (slab_free) {