From: "Dae R. Jeong" <dae.r.jeong@kaist.ac.kr>
Date: Thu, 22 Oct 2020 10:21:28 +0900
Subject: [PATCH] md: fix a warning caused by a race between concurrent
md_ioctl()s
Git-commit: c731b84b51bf7fe83448bea8f56a6d55006b0615
Patch-mainline: v5.11
References: git-fixes
Syzkaller reports a warning as belows.
Warning: CPU: 0 PID: 9647 at drivers/md/md.c:7169
...
Call Trace:
...
Rip: 0010:md_ioctl+0x4017/0x5980 drivers/md/md.c:7169
Rsp: 0018:ffff888096027950 EFLAGS: 00010293
Rax: ffff88809322c380 RBX: 0000000000000932 RCX: ffffffff84e266f2
Rdx: 0000000000000000 RSI: ffffffff84e299f7 RDI: 0000000000000007
Rbp: ffff888096027bc0 R08: ffff88809322c380 R09: ffffed101341a482
R10: ffff888096027940 R11: ffff88809a0d240f R12: 0000000000000932
R13: ffff8880a2c14100 R14: ffff88809a0d2268 R15: ffff88809a0d2408
__blkdev_driver_ioctl block/ioctl.c:304 [inline]
blkdev_ioctl+0xece/0x1c10 block/ioctl.c:606
block_ioctl+0xee/0x130 fs/block_dev.c:1930
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:696
ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
This is caused by a race between two concurrenct md_ioctl()s closing
the array.
CPU1 (md_ioctl()) CPU2 (md_ioctl())
Acked-by: NeilBrown <neilb@suse.com>
Signed-off-by: Neil Brown <neilb@suse.com>
------ ------
set_bit(MD_CLOSING, &mddev->flags);
did_set_md_closing = true;
WARN_ON_ONCE(test_bit(MD_CLOSING,
&mddev->flags));
if(did_set_md_closing)
clear_bit(MD_CLOSING, &mddev->flags);
Fix the warning by returning immediately if the MD_CLOSING bit is set
in &mddev->flags which indicates that the array is being closed.
Fixes: 065e519e71b2 ("md: MD_CLOSING needs to be cleared after called md_set_readonly or do_md_stop")
Reported-by: syzbot+1e46a0864c1a6e9bd3d8@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Dae R. Jeong <dae.r.jeong@kaist.ac.kr>
Signed-off-by: Song Liu <songliubraving@fb.com>
---
drivers/md/md.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7466,8 +7466,11 @@ static int md_ioctl(struct block_device
err = -EBUSY;
goto out;
}
- WARN_ON_ONCE(test_bit(MD_CLOSING, &mddev->flags));
- set_bit(MD_CLOSING, &mddev->flags);
+ if (test_and_set_bit(MD_CLOSING, &mddev->flags)) {
+ mutex_unlock(&mddev->open_mutex);
+ err = -EBUSY;
+ goto out;
+ }
did_set_md_closing = true;
mutex_unlock(&mddev->open_mutex);
sync_blockdev(bdev);