Re: [PATCH] ocfs2: Cancel quota sync work before freeing quota info

[Joseph Qi <joseph.qi@linux.alibaba.com>]

On 10/14/26 11:43 AM, Cen Zhang wrote:
> OCFS2 quota info owns dqi_sync_work and must outlive both its timer
> and qsync_work_fn(). ocfs2_local_free_info() frees that owner without
> cancelling the work, relying on the quota suspend/disable wrappers.
> 
> Loading quotas on a read-only to read-write remount can successfully
> queue the work in ocfs2_global_read_info() and then fail while attaching
> a dquot to an existing inode in add_dquot_ref(). The quota core unwinds
> that failure directly through dquot_disable(), bypassing the OCFS2
> wrapper:
> 
>   Remount task (s_umount write)        Timer/workqueue
>   ocfs2_global_read_info()
>     schedules dqi_sync_work
>   add_dquot_ref() returns an error
>   dquot_disable()
>     ocfs2_local_free_info()
>       frees oinfo
>                                      delayed-work timer expires
>                                      qsync_work_fn() reads oinfo
> 
> The timer core can then write to the freed embedded timer, or
> qsync_work_fn() can read oinfo->dqi_gqinode before its s_umount trylock.
> The outer ocfs2_disable_quotas() cleanup skips the failed type because
> dquot_disable() has already cleared its loaded state.
> 
> Cancel dqi_sync_work synchronously at the start of
> ocfs2_local_free_info(), before dropping the global inode or freeing any
> owner state. The work is initialized whenever read_file_info() succeeds.
> dquot_disable() holds s_umount for write, so the callback skips its quota
> scan via down_read_trylock() and can finish without waiting for teardown.
> The synchronous cancel also handles its self-rearm.
> 
> KASAN report as below:
> 
>     BUG: KASAN: slab-use-after-free in __run_timers+0x9e9/0xa10
>     Write of size 8 at addr ffff888111b0aad0 by task swapper/3/0
> 
>     Call Trace:
>      <IRQ>
>      dump_stack_lvl+0x93/0xd0
>      print_report+0xce/0x630
>      ? __run_timers+0x9e9/0xa10
>      ? srso_alias_return_thunk+0x5/0xfbef5
>      ? __virt_addr_valid+0x20e/0x420
>      ? __run_timers+0x9e9/0xa10
>      kasan_report+0xe0/0x110
>      ? __run_timers+0x9e9/0xa10
>      __run_timers+0x9e9/0xa10
>      ? __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
>      ? ct_kernel_exit.constprop.0+0xc5/0xf0
>      ? do_idle+0x3ae/0x650
>      default_idle+0x9/0x10
>      default_idle_call+0x6c/0xb0
>      do_idle+0x3ae/0x650
>      ? cpuhp_online_idle+0x9c/0xb0
>      ? __pfx_do_idle+0x10/0x10
>      ? __entry_text_end+0x1020f6/0x1020f9
>      ? lockdep_hardirqs_on_prepare+0xeb/0x1a0
>      ? srso_alias_return_thunk+0x5/0xfbef5
>      ? trace_hardirqs_on+0x18/0x160
>      ? srso_alias_return_thunk+0x5/0xfbef5
>      cpu_startup_entry+0x54/0x60
>      start_secondary+0x223/0x2d0
>      ? __pfx_start_secondary+0x10/0x10
>      common_startup_64+0x13e/0x158
>      </TASK>
> 
>     Allocated by task 523:
>      kasan_save_stack+0x33/0x60
>      kasan_save_track+0x14/0x30
>      __kasan_kmalloc+0xaa/0xb0
>      __kmalloc_cache_noprof+0x28d/0x610
>      ocfs2_local_read_info+0x181/0x1580
>      dquot_load_quota_sb+0x69e/0x11c0
>      dquot_load_quota_inode+0x227/0x3e0
>      ocfs2_enable_quotas+0x27c/0x520
>      ocfs2_reconfigure+0x964/0xd00
>      reconfigure_super+0x3ca/0xa70
>      path_mount+0x141e/0x1e80
>      __x64_sys_mount+0x24b/0x2d0
>      do_syscall_64+0x114/0x620
>      entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
>     Freed by task 523:
>      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_local_free_info+0x47b/0x800
>      dquot_disable+0x5d9/0x17a0
>      dquot_load_quota_sb+0xd3c/0x11c0
>      dquot_load_quota_inode+0x227/0x3e0
>      ocfs2_enable_quotas+0x27c/0x520
>      ocfs2_reconfigure+0x964/0xd00
>      reconfigure_super+0x3ca/0xa70
>      path_mount+0x141e/0x1e80
>      __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 ffff888111b0a800
>      which belongs to the cache kmalloc-1k of size 1024
>     The buggy address is located 720 bytes inside of
>      freed 1024-byte region [ffff888111b0a800, ffff888111b0ac00)
> 
> Host details, register and page dumps omitted.
> 
> Fixes: 1a6152d36dee ("quota: propagate error from __dquot_initialize")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Cen Zhang <zzzccc427@gmail.com>

Looks fine.
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>

> Assisted-by: LLM
> 
> ---
> diff --git a/fs/ocfs2/quota_local.c b/fs/ocfs2/quota_local.c
> index 76e7dd5aecc8..a2ce25a33607 100644
> --- a/fs/ocfs2/quota_local.c
> +++ b/fs/ocfs2/quota_local.c
> @@ -840,6 +840,9 @@ static int ocfs2_local_free_info(struct super_block *sb, int type)
>  	int mark_clean = 1, len;
>  	int status = 0;
>  
> +	/* Quota-core error paths can bypass ocfs2_disable_quotas(). */
> +	cancel_delayed_work_sync(&oinfo->dqi_sync_work);
> +
>  	iput(oinfo->dqi_gqinode);
>  	ocfs2_simple_drop_lockres(OCFS2_SB(sb), &oinfo->dqi_gqlock);
>  	ocfs2_lock_res_free(&oinfo->dqi_gqlock);