Concurrent processes md_stop and IO submitting could trigger a
null-ptr-deref of 'mddev->private':
BUG: kernel NULL pointer dereference, address: 0000000000000070
RIP: 0010:_wait_barrier+0x2f/0x250
Call Trace:
raid1_make_request+0x150/0xf50
md_handle_request+0x104/0x530
md_submit_bio+0x76/0x130
submit_bio+0xdd/0x250
submit_bio_wait+0x1f/0x40
__blkdev_direct_IO_simple+0x1f6/0x370
blkdev_write_iter+0x3b2/0x520
ksys_write+0x7d/0x190
P1
fd = open(/dev/md0, O_RDWR)
P2 (forked from P1, fd' <= fd)
write(fd)
submit_bio
md_handle_request
raid1_make_request
raid1_write_request
ioctl(fd, STOP_ARRAY)
mddev_set_closing_and_sync_blockdev
// check passed, mddev->openers = 1,
// because md_open() is only called
// once in P1->open
do_md_stop
__md_stop
mddev->private = NULL
conf = mddev->private // NULL
wait_barrier(conf, sector) // null-ptr-deref !
It is a common problem for raid0/1/10/5, and __md_stop could be
triggered by several paths(eg. ioctl, sysfs, ->dtr). Fix it by
replacing mddev_lock() with mddev_suspend_and_lock() for all
__md_stop() callers.
Fetch a reproducer in https://bugzilla.kernel.org/show_bug.cgi?id=222020
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=3fe892ea5fc292e1353f
Signed-off-by: Zhihao Cheng <[email protected]>
---
drivers/md/dm-raid.c | 7 +++++--
drivers/md/md.c | 18 +++++++++++++++---
2 files changed, 20 insertions(+), 5 deletions(-)
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 8f5a5e1342a9..3dda494fe172 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3326,12 +3326,15 @@ static int raid_ctr(struct dm_target *ti, unsigned int
argc, char **argv)
static void raid_dtr(struct dm_target *ti)
{
+ unsigned int noio_flags = 0;
struct raid_set *rs = ti->private;
- mddev_lock_nointr(&rs->md);
+ mddev_suspend_and_lock_nointr(&rs->md);
+ noio_flags = memalloc_noio_save();
md_stop(&rs->md);
rs->md.dm_gendisk = NULL;
- mddev_unlock(&rs->md);
+ memalloc_noio_restore(noio_flags);
+ mddev_unlock_and_resume(&rs->md);
if (work_pending(&rs->md.event_work))
flush_work(&rs->md.event_work);
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 680b34a63cb3..e292acd54bb0 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4657,6 +4657,8 @@ array_state_store(struct mddev *mddev, const char *buf,
size_t len)
{
int err = 0;
enum array_state st = match_word(buf, array_states);
+ unsigned int noio_flags = 0;
+ bool suspend = false;
/* No lock dependent actions */
switch (st) {
@@ -4666,9 +4668,11 @@ array_state_store(struct mddev *mddev, const char *buf,
size_t len)
case broken: /* cannot be set */
case bad_word:
return -EINVAL;
+ case inactive:
case clear:
+ suspend = true;
+ fallthrough;
case readonly:
- case inactive:
case read_auto:
if (!mddev->pers || !md_is_rdwr(mddev))
break;
@@ -4702,9 +4706,11 @@ array_state_store(struct mddev *mddev, const char *buf,
size_t len)
spin_unlock(&mddev->lock);
return err ?: len;
}
- err = mddev_lock(mddev);
+ err = suspend ? mddev_suspend_and_lock(mddev) : mddev_lock(mddev);
if (err)
return err;
+ if (suspend)
+ noio_flags = memalloc_noio_save();
switch (st) {
case inactive:
@@ -4775,7 +4781,12 @@ array_state_store(struct mddev *mddev, const char *buf,
size_t len)
mddev->hold_active = 0;
sysfs_notify_dirent_safe(mddev->sysfs_state);
}
- mddev_unlock(mddev);
+ if (suspend) {
+ memalloc_noio_restore(noio_flags);
+ mddev_unlock_and_resume(mddev);
+ } else {
+ mddev_unlock(mddev);
+ }
if (st == readonly || st == read_auto || st == inactive ||
(err && st == clear))
@@ -8299,6 +8310,7 @@ static bool md_ioctl_need_suspend(unsigned int cmd)
case HOT_REMOVE_DISK:
case SET_BITMAP_FILE:
case SET_ARRAY_INFO:
+ case STOP_ARRAY:
return true;
default:
return false;
--
2.52.0
