[dm-devel] + dm-fix-find_device-race.patch added to -mm tree

[akpm at osdl.org]

The patch titled
     dm: fix find_device race
has been added to the -mm tree.  Its filename is
     dm-fix-find_device-race.patch

See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this

------------------------------------------------------
Subject: dm: fix find_device race
From: Alasdair G Kergon <agk at redhat.com>

There is a race between dev_create() and find_device().

If the mdptr has not yet been stored against a device, find_device() needs to
behave as though no device was found.  It already returns NULL, but there is a
dm_put() missing: it must drop the reference dm_get_md() took.

The bug was introduced by dm-fix-mapped-device-ref-counting.patch.

It manifests itself if another dm ioctl attempts to reference a newly-created
device while the device creation ioctl is still running.  The consequence is
that the device cannot be removed until the machine is rebooted.  Certain udev
configurations can lead to this happening.

Signed-off-by: Alasdair G Kergon <agk at redhat.com>
Cc: <dm-devel at redhat.com>
Signed-off-by: Andrew Morton <akpm at osdl.org>
---

 drivers/md/dm-ioctl.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff -puN drivers/md/dm-ioctl.c~dm-fix-find_device-race drivers/md/dm-ioctl.c
--- a/drivers/md/dm-ioctl.c~dm-fix-find_device-race
+++ a/drivers/md/dm-ioctl.c
@@ -606,9 +606,14 @@ static struct hash_cell *__find_device_h
 		return __get_name_cell(param->name);
 
 	md = dm_get_md(huge_decode_dev(param->dev));
-	if (md)
-		mdptr = dm_get_mdptr(md);
+	if (!md)
+		goto out;
 
+	mdptr = dm_get_mdptr(md);
+	if (!mdptr)
+		dm_put(md);
+
+out:
 	return mdptr;
 }
 
_

Patches currently in -mm which might be from agk at redhat.com are

dm-fix-find_device-race.patch
dm-suspend-fix-error-path.patch
dm-multipath-fix-rr_add_path-order.patch
dm-raid1-fix-waiting-for-io-on-suspend.patch
dm-raid1-fix-waiting-for-io-on-suspend-fix.patch
fs-freeze_bdev-with-semaphore-not-mutex.patch
struct-path-rename-dms-struct-path.patch
md-dm-reduce-stack-usage-with-stacked-block-devices.patch