linux-kernel - Re: [PATCH V3 1/1] md/raid1: stop mdx_raid1 thread when raid1 array run failed

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Date:   Wed, 9 Nov 2022 14:09:08 -0800
From:   Song Liu <song@...nel.org>
To:     Jiang Li <jiang.li1388@...il.com>
Cc:     linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        lijiang@...een.com, Jiang Li <jiang.li@...een.com>
Subject: Re: [PATCH V3 1/1] md/raid1: stop mdx_raid1 thread when raid1 array
 run failed

On Mon, Nov 7, 2022 at 6:17 AM Jiang Li <jiang.li1388@...il.com> wrote:
>
> From: Jiang Li <jiang.li@...een.com>
>
> fail run raid1 array when we assemble array with the inactive disk only,
> but the mdx_raid1 thread were not stop, Even if the associated resources
> have been released. it will caused a NULL dereference when we do poweroff.
>
> This causes the following Oops:
>     [  287.587787] BUG: kernel NULL pointer dereference, address: 0000000000000070
>     [  287.594762] #PF: supervisor read access in kernel mode
>     [  287.599912] #PF: error_code(0x0000) - not-present page
>     [  287.605061] PGD 0 P4D 0
>     [  287.607612] Oops: 0000 [#1] SMP NOPTI
>     [  287.611287] CPU: 3 PID: 5265 Comm: md0_raid1 Tainted: G     U            5.10.146 #0
>     [  287.619029] Hardware name: xxxxxxx/To be filled by O.E.M, BIOS 5.19 06/16/2022
>     [  287.626775] RIP: 0010:md_check_recovery+0x57/0x500 [md_mod]
>     [  287.632357] Code: fe 01 00 00 48 83 bb 10 03 00 00 00 74 08 48 89 ......
>     [  287.651118] RSP: 0018:ffffc90000433d78 EFLAGS: 00010202
>     [  287.656347] RAX: 0000000000000000 RBX: ffff888105986800 RCX: 0000000000000000
>     [  287.663491] RDX: ffffc90000433bb0 RSI: 00000000ffffefff RDI: ffff888105986800
>     [  287.670634] RBP: ffffc90000433da0 R08: 0000000000000000 R09: c0000000ffffefff
>     [  287.677771] R10: 0000000000000001 R11: ffffc90000433ba8 R12: ffff888105986800
>     [  287.684907] R13: 0000000000000000 R14: fffffffffffffe00 R15: ffff888100b6b500
>     [  287.692052] FS:  0000000000000000(0000) GS:ffff888277f80000(0000) knlGS:0000000000000000
>     [  287.700149] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>     [  287.705897] CR2: 0000000000000070 CR3: 000000000320a000 CR4: 0000000000350ee0
>     [  287.713033] Call Trace:
>     [  287.715498]  raid1d+0x6c/0xbbb [raid1]
>     [  287.719256]  ? __schedule+0x1ff/0x760
>     [  287.722930]  ? schedule+0x3b/0xb0
>     [  287.726260]  ? schedule_timeout+0x1ed/0x290
>     [  287.730456]  ? __switch_to+0x11f/0x400
>     [  287.734219]  md_thread+0xe9/0x140 [md_mod]
>     [  287.738328]  ? md_thread+0xe9/0x140 [md_mod]
>     [  287.742601]  ? wait_woken+0x80/0x80
>     [  287.746097]  ? md_register_thread+0xe0/0xe0 [md_mod]
>     [  287.751064]  kthread+0x11a/0x140
>     [  287.754300]  ? kthread_park+0x90/0x90
>     [  287.757974]  ret_from_fork+0x1f/0x30
>
> In fact, when raid1 array run fail, we need to do
> md_unregister_thread() before raid1_free().
>
> Signed-off-by: Jiang Li <jiang.li@...een.com>

Applied to md-next. Thanks!
Song

> ---
> Hi,
> my full name is Jiang Li. Thanks!
>
> The following steps can be used to reproduce the problem:
> mdadm --create /dev/md0 --level=1  --raid-devices=2 /dev/sd[a-b]
> mdadm -A /dev/md0 /dev/sd[a-b]
> mkfs.ext4  /dev/md0
> mount /dev/md0   /mnt/md0
>
> mdadm -S /dev/md0
>
> mdadm -A /dev/md0 /dev/sda   --run
> mount /dev/md0   /mnt/md0
> #Store a certain amount of data, so that the rebuilding will not be completed in a short time
> dd if=/dev/urandom of=/mnt/md0/test.db bs=1M count=40960
>
> mdadm --add /dev/md0 /dev/sdb
> sleep 1
> #when the array were rebuilding, we stop the array.
> umount /dev/md0
> mdadm -S  /dev/md0
>
> #assemble array with the sdb only in --run insist mode:
> mdadm -A /dev/md0 /dev/sdb  --run
>
> #md run fail with kernel message as follow:
> [  850.593441] md: md0 stopped.
> [  850.672071] md: pers->run() failed ...
> [  850.686913] md: md0 stopped.
>
> #we can see the md0_raid1 thread were not stop:
> $ps -ef | grep raid1
> root      5672     2  0 Oct31 ?        00:00:04 [md0_raid1]
>
> #now, do poweroff can reproduce the problem.
>
>  drivers/md/raid1.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 05d8438cfec8..58f705f42948 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -3159,6 +3159,7 @@ static int raid1_run(struct mddev *mddev)
>          * RAID1 needs at least one disk in active
>          */
>         if (conf->raid_disks - mddev->degraded < 1) {
> +               md_unregister_thread(&conf->thread);
>                 ret = -EINVAL;
>                 goto abort;
>         }
> --
> 2.25.1
>