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

[Cen Zhang <zzzccc427@gmail.com>]

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>
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);