The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f7c7a2f9a23e5b6e0f5251f29648d0238bb7757e Mon Sep 17 00:00:00 2001

From: Heming Zhao heming.zhao@suse.com Date: Thu, 8 Apr 2021 15:44:15 +0800 Subject: [PATCH] md-cluster: fix use-after-free issue when removing rdev

md_kick_rdev_from_array will remove rdev, so we should use rdev_for_each_safe to search list.

How to trigger:

env: Two nodes on kvm-qemu x86_64 VMs (2C2G with 2 iscsi luns).

``` node2=192.168.0.3

for i in {1..20}; do echo ==== $i `date` ====;

mdadm -Ss && ssh ${node2} "mdadm -Ss" wipefs -a /dev/sda /dev/sdb

mdadm -CR /dev/md0 -b clustered -e 1.2 -n 2 -l 1 /dev/sda \ /dev/sdb --assume-clean ssh ${node2} "mdadm -A /dev/md0 /dev/sda /dev/sdb" mdadm --wait /dev/md0 ssh ${node2} "mdadm --wait /dev/md0"

mdadm --manage /dev/md0 --fail /dev/sda --remove /dev/sda sleep 1 done ```

Crash stack:

``` stack segment: 0000 [#1] SMP ... ... RIP: 0010:md_check_recovery+0x1e8/0x570 [md_mod] ... ... RSP: 0018:ffffb149807a7d68 EFLAGS: 00010207 RAX: 0000000000000000 RBX: ffff9d494c180800 RCX: ffff9d490fc01e50 RDX: fffff047c0ed8308 RSI: 0000000000000246 RDI: 0000000000000246 RBP: 6b6b6b6b6b6b6b6b R08: ffff9d490fc01e40 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000 R13: ffff9d494c180818 R14: ffff9d493399ef38 R15: ffff9d4933a1d800 FS: 0000000000000000(0000) GS:ffff9d494f700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe68cab9010 CR3: 000000004c6be001 CR4: 00000000003706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: raid1d+0x5c/0xd40 [raid1] ? finish_task_switch+0x75/0x2a0 ? lock_timer_base+0x67/0x80 ? try_to_del_timer_sync+0x4d/0x80 ? del_timer_sync+0x41/0x50 ? schedule_timeout+0x254/0x2d0 ? md_start_sync+0xe0/0xe0 [md_mod] ? md_thread+0x127/0x160 [md_mod] md_thread+0x127/0x160 [md_mod] ? wait_woken+0x80/0x80 kthread+0x10d/0x130 ? kthread_park+0xa0/0xa0 ret_from_fork+0x1f/0x40 ```

Fixes: dbb64f8635f5d ("md-cluster: Fix adding of new disk with new reload code") Fixes: 659b254fa7392 ("md-cluster: remove a disk asynchronously from cluster environment") Cc: stable@vger.kernel.org Reviewed-by: Gang He ghe@suse.com Signed-off-by: Heming Zhao heming.zhao@suse.com Signed-off-by: Song Liu song@kernel.org

diff --git a/drivers/md/md.c b/drivers/md/md.c index af9bdb907b2b..49f897fbb89b 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -9289,11 +9289,11 @@ void md_check_recovery(struct mddev *mddev) }

if (mddev_is_clustered(mddev)) { - struct md_rdev *rdev; + struct md_rdev *rdev, *tmp; /* kick the device if another node issued a * remove disk. */ - rdev_for_each(rdev, mddev) { + rdev_for_each_safe(rdev, tmp, mddev) { if (test_and_clear_bit(ClusterRemove, &rdev->flags) && rdev->raid_disk < 0) md_kick_rdev_from_array(rdev); @@ -9607,7 +9607,7 @@ static int __init md_init(void) static void check_sb_changes(struct mddev *mddev, struct md_rdev *rdev) { struct mdp_superblock_1 *sb = page_address(rdev->sb_page); - struct md_rdev *rdev2; + struct md_rdev *rdev2, *tmp; int role, ret; char b[BDEVNAME_SIZE];

@@ -9624,7 +9624,7 @@ static void check_sb_changes(struct mddev *mddev, struct md_rdev *rdev) }

/* Check for change of roles in the active devices */ - rdev_for_each(rdev2, mddev) { + rdev_for_each_safe(rdev2, tmp, mddev) { if (test_bit(Faulty, &rdev2->flags)) continue;