* [PATCH] ocfs2: drain fs_state readers before journal teardown
@ 2026-10-30 5:25 Cen Zhang
0 siblings, 0 replies; only message in thread
From: Cen Zhang @ 2026-10-30 5:25 UTC (permalink / raw)
To: mark, jlbec, joseph.qi
Cc: heming.zhao, ocfs2-devel, linux-kernel, stable, baijiaju1990,
jjzuming, zzzccc427
The per-mount fs_state open callback formats journal fields through
osb->journal. Its debugfs active-user guard protects the open callback,
but does not keep the journal allocated after journal shutdown.
Both unmount and the mount-error path in ocfs2_mount_volume() can free
and clear the journal before the debugfs subtree is removed:
fs_state reader Mount cleanup
--------------- -------------
enter ocfs2_osb_debug_open()
ocfs2_osb_dump()
load osb->journal
ocfs2_journal_shutdown()
free journal; clear pointer
read journal fields
leave the open callback
remove the debugfs subtree
Remove fs_state before cleanup releases its backing state in both
callers of ocfs2_journal_shutdown(). Debugfs removal prevents new opens
and waits for admitted open callbacks to finish. Later reads and release
use only the per-open snapshot buffer, so they do not need the journal.
Keep removal in the caller paths while the per-mount debugfs parent is
still present. The remaining debug files retain their teardown order.
KASAN report as below:
BUG: KASAN: slab-use-after-free in ocfs2_osb_debug_open+0x967/0x15e0
Read of size 4 at addr ffff888116a56028 by task cat/502
CPU: 3 UID: 0 PID: 502 Comm: cat Not tainted 7.3.0-rc4-next-20260921-pmb-ocfs2-functional-v1+ #1 PREEMPT(lazy)
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x93/0xd0
print_report+0xce/0x630
? ocfs2_osb_debug_open+0x967/0x15e0
? srso_alias_return_thunk+0x5/0xfbef5
? __virt_addr_valid+0x20e/0x420
? ocfs2_osb_debug_open+0x967/0x15e0
kasan_report+0xe0/0x110
? ocfs2_osb_debug_open+0x967/0x15e0
kasan_check_range+0x105/0x1b0
ocfs2_osb_debug_open+0x967/0x15e0
? __pfx_ocfs2_osb_debug_open+0x10/0x10
full_proxy_open_regular+0x193/0x310
do_dentry_open+0x595/0x12d0
? __pfx_full_proxy_open_regular+0x10/0x10
vfs_open_consume+0xd1/0x400
? srso_alias_return_thunk+0x5/0xfbef5
path_openat+0x18d0/0x2020
? __pfx_path_openat+0x10/0x10
do_file_open+0x21e/0x470
? __pfx_do_file_open+0x10/0x10
? _raw_spin_unlock+0x23/0x40
? srso_alias_return_thunk+0x5/0xfbef5
? alloc_fd+0x3a6/0x6b0
do_sys_openat2+0xf4/0x1b0
? __pfx_do_sys_openat2+0x10/0x10
? __pfx___do_sys_newfstat+0x10/0x10
__x64_sys_openat+0x136/0x1e0
? __pfx___x64_sys_openat+0x10/0x10
? irqentry_exit+0xbe/0x820
? srso_alias_return_thunk+0x5/0xfbef5
? trace_hardirqs_on_prepare+0x11d/0x150
? srso_alias_return_thunk+0x5/0xfbef5
do_syscall_64+0x114/0x620
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7d444d6687
Code: 48 89 fa 4c 89 df e8 58 b3 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fff1e988040 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f7d44444780 RCX: 00007f7d444d6687
RDX: 0000000000000000 RSI: 00007fff1e988df7 RDI: ffffffffffffff9c
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000560ae86f2a00
R13: 00007fff1e988380 R14: 0000000000000000 R15: 0000000000040000
</TASK>
Allocated by task 495:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
__kasan_kmalloc+0xaa/0xb0
__kmalloc_cache_noprof+0x28d/0x610
ocfs2_journal_alloc+0x91/0x450
ocfs2_initialize_super.isra.0+0x11b8/0x3070
ocfs2_fill_super+0x801/0x38f0
get_tree_bdev_flags+0x35d/0x5f0
vfs_get_tree+0x93/0x320
fc_mount+0x1d/0x200
path_mount+0x592/0x1e00
__x64_sys_mount+0x24b/0x2d0
do_syscall_64+0x114/0x620
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 504:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3b/0x60
__kasan_slab_free+0x5f/0x80
kfree+0x308/0x580
ocfs2_journal_shutdown+0x10a/0xc20
ocfs2_dismount_volume+0x315/0x940
generic_shutdown_super+0x15f/0x490
kill_block_super+0x40/0xa0
deactivate_locked_super+0xae/0x120
deactivate_super+0xa2/0xc0
cleanup_mnt+0x217/0x450
task_work_run+0x144/0x230
exit_to_user_mode_loop+0x17d/0x570
do_syscall_64+0x4d1/0x620
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Last potentially related work creation:
kasan_save_stack+0x33/0x60
kasan_record_aux_stack+0xa7/0xc0
insert_work+0x37/0x210
__queue_work+0xb57/0x1600
queue_work_on+0xda/0xf0
ocfs2_queue_recovery_completion+0x301/0x480
ocfs2_complete_mount_recovery+0x10c/0x290
ocfs2_fill_super+0x2083/0x38f0
get_tree_bdev_flags+0x35d/0x5f0
vfs_get_tree+0x93/0x320
fc_mount+0x1d/0x200
path_mount+0x592/0x1e00
__x64_sys_mount+0x24b/0x2d0
do_syscall_64+0x114/0x620
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff888116a56000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 40 bytes inside of
freed 512-byte region [ffff888116a56000, ffff888116a56200)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x116a54
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x200000000000040(head|node=0|zone=2)
page_type: f5(slab)
raw: 0200000000000040 ffff888100042c80 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 0200000000000040 ffff888100042c80 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 0200000000000002 ffffffffffffff01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888116a55f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888116a55f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888116a56000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888116a56080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888116a56100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Fixes: da5e7c87827e ("ocfs2: cleanup journal init and shutdown")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Cen Zhang <zzzccc427@gmail.com>
---
fs/ocfs2/super.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 0af2245ae303..9f93ae9433c2 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -1783,6 +1783,9 @@ static int ocfs2_mount_volume(struct super_block *sb)
return 0;
out_system_inodes:
+ /* Drain fs_state readers before releasing their backing state. */
+ debugfs_lookup_and_remove("fs_state", osb->osb_debug_root);
+
if (osb->local_alloc_state == OCFS2_LA_ENABLED)
ocfs2_shutdown_local_alloc(osb);
/* Drain pending suballoc reclaim work before the journal goes away */
@@ -1810,6 +1813,9 @@ static void ocfs2_dismount_volume(struct super_block *sb, int mnt_err)
BUG_ON(!sb);
osb = OCFS2_SB(sb);
+
+ /* Drain fs_state readers before releasing their backing state. */
+ debugfs_lookup_and_remove("fs_state", osb->osb_debug_root);
BUG_ON(!osb);
/* Remove file check sysfs related directories/files,
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