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

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Message-Id: <20221107141659.2680-1-jiang.li1388@gmail.com>
Date:   Mon,  7 Nov 2022 22:16:59 +0800
From:   Jiang Li <jiang.li1388@...il.com>
To:     song@...nel.org
Cc:     linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        lijiang@...een.com, Jiang Li <jiang.li@...een.com>
Subject: [PATCH V3 1/1] md/raid1: stop mdx_raid1 thread when raid1 array run failed

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>
---
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