[dm-devel] [PATCH] md-raid: destroy the bitmap after destroying the thread

[Song Liu]

On Sun, Jul 24, 2022 at 11:26 AM Mikulas Patocka <mpatocka at redhat.com> wrote:
>
> When we ran the lvm test "shell/integrity-blocksize-3.sh" on a kernel with
> kasan, we got failure in write_page.
>
> The reason for the failure is that md_bitmap_destroy is called before
> destroying the thread and the thread may be waiting in the function
> write_page for the bio to complete. When the thread finishes waiting, it
> executes "if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))", which
> triggers the kasan warning.
>
> Note that the commit 48df498daf62 that caused this bug claims that it is
> neede for md-cluster, you should check md-cluster and possibly find
> another bugfix for it.
>
> BUG: KASAN: use-after-free in write_page+0x18d/0x680 [md_mod]
> Read of size 8 at addr ffff889162030c78 by task mdX_raid1/5539
>
> CPU: 10 PID: 5539 Comm: mdX_raid1 Not tainted 5.19.0-rc2 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x34/0x44
>  print_report.cold+0x45/0x57a
>  ? __lock_text_start+0x18/0x18
>  ? write_page+0x18d/0x680 [md_mod]
>  kasan_report+0xa8/0xe0
>  ? write_page+0x18d/0x680 [md_mod]
>  kasan_check_range+0x13f/0x180
>  write_page+0x18d/0x680 [md_mod]
>  ? super_sync+0x4d5/0x560 [dm_raid]
>  ? md_bitmap_file_kick+0xa0/0xa0 [md_mod]
>  ? rs_set_dev_and_array_sectors+0x2e0/0x2e0 [dm_raid]
>  ? mutex_trylock+0x120/0x120
>  ? preempt_count_add+0x6b/0xc0
>  ? preempt_count_sub+0xf/0xc0
>  md_update_sb+0x707/0xe40 [md_mod]
>  md_reap_sync_thread+0x1b2/0x4a0 [md_mod]
>  md_check_recovery+0x533/0x960 [md_mod]
>  raid1d+0xc8/0x2a20 [raid1]
>  ? var_wake_function+0xe0/0xe0
>  ? psi_group_change+0x411/0x500
>  ? preempt_count_sub+0xf/0xc0
>  ? _raw_spin_lock_irqsave+0x78/0xc0
>  ? __lock_text_start+0x18/0x18
>  ? raid1_end_read_request+0x2a0/0x2a0 [raid1]
>  ? preempt_count_sub+0xf/0xc0
>  ? _raw_spin_unlock_irqrestore+0x19/0x40
>  ? del_timer_sync+0xa9/0x100
>  ? try_to_del_timer_sync+0xc0/0xc0
>  ? _raw_spin_lock_irqsave+0x78/0xc0
>  ? __lock_text_start+0x18/0x18
>  ? __list_del_entry_valid+0x68/0xa0
>  ? finish_wait+0xa3/0x100
>  md_thread+0x161/0x260 [md_mod]
>  ? unregister_md_personality+0xa0/0xa0 [md_mod]
>  ? _raw_spin_lock_irqsave+0x78/0xc0
>  ? prepare_to_wait_event+0x2c0/0x2c0
>  ? unregister_md_personality+0xa0/0xa0 [md_mod]
>  kthread+0x148/0x180
>  ? kthread_complete_and_exit+0x20/0x20
>  ret_from_fork+0x1f/0x30
>  </TASK>
>
> Allocated by task 5522:
>  kasan_save_stack+0x1e/0x40
>  __kasan_kmalloc+0x80/0xa0
>  md_bitmap_create+0xa8/0xe80 [md_mod]
>  md_run+0x777/0x1300 [md_mod]
>  raid_ctr+0x249c/0x4a30 [dm_raid]
>  dm_table_add_target+0x2b0/0x620 [dm_mod]
>  table_load+0x1c8/0x400 [dm_mod]
>  ctl_ioctl+0x29e/0x560 [dm_mod]
>  dm_compat_ctl_ioctl+0x7/0x20 [dm_mod]
>  __do_compat_sys_ioctl+0xfa/0x160
>  do_syscall_64+0x90/0xc0
>  entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
> Freed by task 5680:
>  kasan_save_stack+0x1e/0x40
>  kasan_set_track+0x21/0x40
>  kasan_set_free_info+0x20/0x40
>  __kasan_slab_free+0xf7/0x140
>  kfree+0x80/0x240
>  md_bitmap_free+0x1c3/0x280 [md_mod]
>  __md_stop+0x21/0x120 [md_mod]
>  md_stop+0x9/0x40 [md_mod]
>  raid_dtr+0x1b/0x40 [dm_raid]
>  dm_table_destroy+0x98/0x1e0 [dm_mod]
>  __dm_destroy+0x199/0x360 [dm_mod]
>  dev_remove+0x10c/0x160 [dm_mod]
>  ctl_ioctl+0x29e/0x560 [dm_mod]
>  dm_compat_ctl_ioctl+0x7/0x20 [dm_mod]
>  __do_compat_sys_ioctl+0xfa/0x160
>  do_syscall_64+0x90/0xc0
>  entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
> Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
> Cc: stable at vger.kernel.org
> Fixes: 48df498daf62 ("md: move bitmap_destroy to the beginning of __md_stop")

Applied to md-next.

Thanks,
Song

>
> ---
>  drivers/md/md.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6/drivers/md/md.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/md.c      2022-06-08 15:39:08.000000000 +0200
> +++ linux-2.6/drivers/md/md.c   2022-06-24 20:22:34.000000000 +0200
> @@ -6244,11 +6244,11 @@ static void mddev_detach(struct mddev *m
>  static void __md_stop(struct mddev *mddev)
>  {
>         struct md_personality *pers = mddev->pers;
> -       md_bitmap_destroy(mddev);
>         mddev_detach(mddev);
>         /* Ensure ->event_work is done */
>         if (mddev->event_work.func)
>                 flush_workqueue(md_misc_wq);
> +       md_bitmap_destroy(mddev);
>         spin_lock(&mddev->lock);
>         mddev->pers = NULL;
>         spin_unlock(&mddev->lock);
>