From: Joseph Qi <joseph.qi@linux.alibaba.com>
To: Cen Zhang <zzzccc427@gmail.com>
Cc: mark@fasheh.com, jlbec@evilplan.org, heming.zhao@suse.com,
ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, baijiaju1990@gmail.com,
jjzuming@gmail.com
Subject: Re: [PATCH] ocfs2: wait for filecheck kobject release after a failed add
Date: Sat, 24 Oct 2026 23:49:37 +0800 [thread overview]
Message-ID: <1868bdad-cad5-4cec-8d76-af6f3cd92479@linux.alibaba.com> (raw)
In-Reply-To: <pm-ocfs2-objects-candidate-0087-v5-4888399e71ae6d93613f@gmail.com>
On 10/22/26 6:56 PM, Cen Zhang wrote:
> The filecheck kobject and its release completion are embedded in
> ocfs2_super, so the osb must outlive the kobject. On a failed
> kobject_init_and_add(), creation clears fs_fcheck and calls
> kobject_put(), but returns without waiting for the release callback.
>
> With CONFIG_DEBUG_KOBJECT_RELEASE, the last put queues delayed cleanup.
> Mount failure can then free the containing osb before the embedded
> release timer expires:
>
> Mount failure Delayed cleanup
> ------------- ---------------
> ocfs2_filecheck_create_sysfs()
> kobject_init_and_add() fails
> fs_fcheck = NULL
> kobject_put()
> queue delayed release
> return to mount error cleanup
> ocfs2_dismount_volume()
> remove_sysfs() skips the wait
> kfree(osb)
> expire embedded release timer
> access freed osb
>
> The normal removal path waits for fs_kobj_unregister, but it returns
> early when fs_fcheck is NULL. The failed-add path therefore leaves the
> delayed work and its completion in freed storage.
>
> Wait for the existing release completion after the failed-add
> kobject_put(), before returning to mount error cleanup. This keeps the
> enclosing osb alive until the kobject has finished releasing, matching
> the normal teardown path.
>
> KASAN report as below:
>
> BUG: KASAN: slab-use-after-free in __run_timers+0xa6d/0xa90
> Write of size 8 at addr ffff8881178a5658 by task swapper/0/0
>
> CPU: 0 UID: 0 PID: 0 Comm: swapper/0 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:
> <IRQ>
> dump_stack_lvl+0x93/0xd0
> print_report+0xce/0x630
> ? __run_timers+0xa6d/0xa90
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? __virt_addr_valid+0x20e/0x420
> ? __run_timers+0xa6d/0xa90
> kasan_report+0xe0/0x110
> ? __run_timers+0xa6d/0xa90
> __run_timers+0xa6d/0xa90
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? __pfx___run_timers+0x10/0x10
> ? __lock_acquire+0x5a3/0x2140
> ? __pfx_do_raw_spin_lock+0x10/0x10
> ? srso_alias_return_thunk+0x5/0xfbef5
> timer_expire_remote+0xfa/0x160
> ? __pfx_timer_expire_remote+0x10/0x10
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? trace_hardirqs_on+0x18/0x160
> tmigr_handle_remote_up+0x4ba/0x9d0
> ? __pfx_tmigr_handle_remote_up+0x10/0x10
> ? tmigr_handle_remote+0x21a/0x340
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? lock_release+0xc8/0x290
> ? __pfx_tmigr_handle_remote_up+0x10/0x10
> __walk_groups_from+0x5a/0x160
> tmigr_handle_remote+0x24f/0x340
> ? __pfx_tmigr_handle_remote+0x10/0x10
> ? lock_acquire+0x190/0x300
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? lock_release+0xc8/0x290
> run_timer_softirq+0x222/0x270
> ? __pfx_run_timer_softirq+0x10/0x10
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? lockdep_hardirqs_on_prepare+0xb8/0x1a0
> ? srso_alias_return_thunk+0x5/0xfbef5
> handle_softirqs+0x1fa/0x8d0
> ? __pfx_handle_softirqs+0x10/0x10
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? _raw_spin_unlock+0x23/0x40
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? __hrtimer_rearm_deferred+0x1fb/0x5d0
> __irq_exit_rcu+0x113/0x1e0
> irq_exit_rcu+0xe/0x20
> sysvec_apic_timer_interrupt+0x6c/0x80
> </IRQ>
> <TASK>
> asm_sysvec_apic_timer_interrupt+0x1a/0x20
> RIP: 0010:pv_native_safe_halt+0xf/0x20
> Code: fa 18 01 e9 ee 37 ff fa 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d 23 c7 14 00 fb f4 <e9> c7 37 ff fa 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
> RSP: 0018:ffffffff87c07cf8 EFLAGS: 00000206
> RAX: 0000000000045d0f RBX: ffffffff87c2d4c0 RCX: ffffffff86111e95
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff815b508e
> RBP: fffffbfff0f85a98 R08: 0000000000000001 R09: ffffed10310c68ba
> R10: ffff8881886345d3 R11: 0000000000000000 R12: 0000000000000001
> R13: 0000000000000000 R14: 1ffffffff0f80fa4 R15: dffffc0000000000
> ? ct_kernel_exit.constprop.0+0xc5/0xf0
> ? do_idle+0x3ae/0x650
> default_idle+0x9/0x10
> default_idle_call+0x6c/0xb0
> do_idle+0x3ae/0x650
> ? __pfx___schedule+0x10/0x10
> ? __pfx_do_idle+0x10/0x10
> ? rest_init+0x1cd/0x330
> ? srso_alias_return_thunk+0x5/0xfbef5
> cpu_startup_entry+0x54/0x60
> rest_init+0x1e1/0x330
> ? __pfx_acpi_read_bit_register+0x10/0x10
> ? __pfx_rest_init+0x10/0x10
> ? acpi_os_write_port+0x23/0xb0
> ? __pfx_kernel_init+0x10/0x10
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? acpi_ut_status_exit+0xd6/0x180
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? acpi_ut_status_exit+0xd6/0x180
> ? srso_alias_return_thunk+0x5/0xfbef5
> ? acpi_enable_subsystem+0x2b0/0x4e0
> ? __pfx_x86_late_time_init+0x10/0x10
> start_kernel+0x417/0x4b0
> x86_64_start_reservations+0x18/0x30
> x86_64_start_kernel+0x111/0x120
> common_startup_64+0x13e/0x158
> </TASK>
>
> Allocated by task 494:
> kasan_save_stack+0x33/0x60
> kasan_save_track+0x14/0x30
> __kasan_kmalloc+0xaa/0xb0
> __kmalloc_cache_noprof+0x28d/0x610
> ocfs2_initialize_super.isra.0+0xab/0x3070
> ocfs2_fill_super+0x801/0x3920
> 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 494:
> 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_dismount_volume+0x43c/0x9b0
> ocfs2_fill_super+0x258f/0x3920
> 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 ffff8881178a4000
> which belongs to the cache kmalloc-8k of size 8192
> The buggy address is located 5720 bytes inside of
> freed 8192-byte region [ffff8881178a4000, ffff8881178a6000)
>
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1178a0
> head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> flags: 0x200000000000040(head|node=0|zone=2)
> page_type: f5(slab)
> raw: 0200000000000040 ffff888100043880 dead000000000122 0000000000000000
> raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
> head: 0200000000000040 ffff888100043880 dead000000000122 0000000000000000
> head: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
> head: 0200000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
> head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff8881178a5500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881178a5580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff8881178a5600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff8881178a5680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881178a5700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
> Fixes: b9fba67b3806 ("ocfs2: fix error path kobject memory leak")
> Cc: stable@vger.kernel.org
> Assisted-by: LLM
> Signed-off-by: Cen Zhang <zzzccc427@gmail.com>
>
> ---
> fs/ocfs2/filecheck.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/ocfs2/filecheck.c b/fs/ocfs2/filecheck.c
> index 75334e4bd082..7e547769beb2 100644
> --- a/fs/ocfs2/filecheck.c
> +++ b/fs/ocfs2/filecheck.c
> @@ -189,6 +189,8 @@ int ocfs2_filecheck_create_sysfs(struct ocfs2_super *osb)
> /* Mount failure still calls ocfs2_filecheck_remove_sysfs(). */
> entry->fs_fcheck = NULL;
> kobject_put(&entry->fs_kobj);
> + /* Drain delayed release before freeing the embedded kobject owner. */
Why not name the owner directly to ocfs2_super?
And "delayed release" is only accurate under CONFIG_DEBUG_KOBJECT_RELEASE.
Thanks,
Joseph
> + wait_for_completion(&entry->fs_kobj_unregister);
> kfree(fcheck);
> return ret;
> }
next prev parent reply other threads:[~2026-10-24 15:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-22 10:56 Cen Zhang
2026-10-24 15:49 ` Joseph Qi [this message]
2026-10-24 16:18 ` Cen Zhang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1868bdad-cad5-4cec-8d76-af6f3cd92479@linux.alibaba.com \
--to=joseph.qi@linux.alibaba.com \
--cc=baijiaju1990@gmail.com \
--cc=heming.zhao@suse.com \
--cc=jjzuming@gmail.com \
--cc=jlbec@evilplan.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark@fasheh.com \
--cc=ocfs2-devel@lists.linux.dev \
--cc=stable@vger.kernel.org \
--cc=zzzccc427@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®