[PATCH 4.19 034/168] md-cluster: fix wild pointer of unlock_all_bitmaps()

Greg Kroah-Hartman
2020-08-17T17:49:15Z

From: Zhao Heming <heming.zhao@suse.com>

[ Upstream commit 60f80d6f2d07a6d8aee485a1d1252327eeee0c81 ]

reproduction steps:
```
node1 # mdadm -C /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sda
/dev/sdb
node2 # mdadm -A /dev/md0 /dev/sda /dev/sdb
node1 # mdadm -G /dev/md0 -b none
mdadm: failed to remove clustered bitmap.
node1 # mdadm -S --scan
^C <==== mdadm hung & kernel crash
```

kernel stack:
```
[ 335.230657] general protection fault: 0000 [#1] SMP NOPTI
[...]
[ 335.230848] Call Trace:
[ 335.230873] ? unlock_all_bitmaps+0x5/0x70 [md_cluster]
[ 335.230886] unlock_all_bitmaps+0x3d/0x70 [md_cluster]
[ 335.230899] leave+0x10f/0x190 [md_cluster]
[ 335.230932] ? md_super_wait+0x93/0xa0 [md_mod]
[ 335.230947] ? leave+0x5/0x190 [md_cluster]
[ 335.230973] md_cluster_stop+0x1a/0x30 [md_mod]
[ 335.230999] md_bitmap_free+0x142/0x150 [md_mod]
[ 335.231013] ? _cond_resched+0x15/0x40
[ 335.231025] ? mutex_lock+0xe/0x30
[ 335.231056] __md_stop+0x1c/0xa0 [md_mod]
[ 335.231083] do_md_stop+0x160/0x580 [md_mod]
[ 335.231119] ? 0xffffffffc05fb078
[ 335.231148] md_ioctl+0xa04/0x1930 [md_mod]
[ 335.231165] ? filename_lookup+0xf2/0x190
[ 335.231179] blkdev_ioctl+0x93c/0xa10
[ 335.231205] ? _cond_resched+0x15/0x40
[ 335.231214] ? __check_object_size+0xd4/0x1a0
[ 335.231224] block_ioctl+0x39/0x40
[ 335.231243] do_vfs_ioctl+0xa0/0x680
[ 335.231253] ksys_ioctl+0x70/0x80
[ 335.231261] __x64_sys_ioctl+0x16/0x20
[ 335.231271] do_syscall_64+0x65/0x1f0
[ 335.231278] entry_SYSCALL_64_after_hwframe+0x44/0xa9
```

Signed-off-by: Zhao Heming <heming.zhao@suse.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/md-cluster.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
index 0b2af6e74fc37..4522e87d9d68d 100644
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -1443,6 +1443,7 @@ static void unlock_all_bitmaps(struct mddev *mddev)
}
}
kfree(cinfo->other_bitmap_lockres);
+ cinfo->other_bitmap_lockres = NULL;
}
}

--
2.25.1