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* [PATCH] ocfs2: wait for filecheck kobject release after a failed add
@ 2026-10-22 10:56 Cen Zhang
  2026-10-24 15:49 ` Joseph Qi
  0 siblings, 1 reply; 3+ messages in thread
From: Cen Zhang @ 2026-10-22 10:56 UTC (permalink / raw)
  To: mark, jlbec, joseph.qi
  Cc: heming.zhao, ocfs2-devel, linux-kernel, stable, baijiaju1990,
	jjzuming, zzzccc427

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. */
+		wait_for_completion(&entry->fs_kobj_unregister);
 		kfree(fcheck);
 		return ret;
 	}

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-10-24 16:18 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2026-10-22 10:56 [PATCH] ocfs2: wait for filecheck kobject release after a failed add Cen Zhang
2026-10-24 15:49 ` Joseph Qi
2026-10-24 16:18   ` Cen Zhang

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