[PATCH 4.14 140/343] drivers/rapidio/rio_cm.c: fix potential oops in riocm_ch_listen()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ Upstream commit 5ac188b12e7cbdd92dee60877d1fac913fc1d074 ]

If riocm_get_channel() fails, then we should just return -EINVAL.
Calling riocm_put_channel() will trigger a NULL dereference and
generally we should call put() if the get() didn't succeed.

Link: http://lkml.kernel.org/r/20190110130230.GB27017@kadam
Fixes: b6e8d4aa1110 ("rapidio: add RapidIO channelized messaging driver")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Porter <mporter@xxxxxxxxxxxxxxxxxxx>
Cc: Alexandre Bounine <alexandre.bounine@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/rapidio/rio_cm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/rapidio/rio_cm.c b/drivers/rapidio/rio_cm.c
index ef989a15aefc4..b29fc258eeba4 100644
--- a/drivers/rapidio/rio_cm.c
+++ b/drivers/rapidio/rio_cm.c
@@ -1215,7 +1215,9 @@ static int riocm_ch_listen(u16 ch_id)
 	riocm_debug(CHOP, "(ch_%d)", ch_id);
 
 	ch = riocm_get_channel(ch_id);
-	if (!ch || !riocm_cmp_exch(ch, RIO_CM_CHAN_BOUND, RIO_CM_LISTEN))
+	if (!ch)
+		return -EINVAL;
+	if (!riocm_cmp_exch(ch, RIO_CM_CHAN_BOUND, RIO_CM_LISTEN))
 		ret = -EINVAL;
 	riocm_put_channel(ch);
 	return ret;
-- 
2.20.1