[PATCH] md/md-multipath: guard against a possible NULL dereference

[Daniil Tatianin]

mempool_alloc might fail to allocate a slot, in which case we will end
up dereferencing a NULL mp_bh pointer.

Found by Linux Verification Center (linuxtesting.org) with the SVACE
static analysis tool.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Daniil Tatianin <d-tatianin@xxxxxxxxxxxxxx>
---
 drivers/md/md-multipath.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/md/md-multipath.c b/drivers/md/md-multipath.c
index 66edf5e72bd6..861c70e49bcc 100644
--- a/drivers/md/md-multipath.c
+++ b/drivers/md/md-multipath.c
@@ -108,6 +108,8 @@ static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
 		return true;
 
 	mp_bh = mempool_alloc(&conf->pool, GFP_NOIO);
+	if (!map_bh)
+		return false;
 
 	mp_bh->master_bio = bio;
 	mp_bh->mddev = mddev;
-- 
2.25.1