[PATCH 5.16 0959/1017] can: isotp: restore accidentally removed MSG_PEEK feature

[Greg Kroah-Hartman]

From: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>

[ Upstream commit e382fea8ae54f5bb62869c6b69b33993d43adeca ]

In commit 42bf50a1795a ("can: isotp: support MSG_TRUNC flag when
reading from socket") a new check for recvmsg flags has been
introduced that only checked for the flags that are handled in
isotp_recvmsg() itself.

This accidentally removed the MSG_PEEK feature flag which is processed
later in the call chain in __skb_try_recv_from_queue().

Add MSG_PEEK to the set of valid flags to restore the feature.

Fixes: 42bf50a1795a ("can: isotp: support MSG_TRUNC flag when reading from socket")
Link: https://github.com/linux-can/can-utils/issues/347#issuecomment-1079554254
Link: https://lore.kernel.org/all/20220328113611.3691-1-socketcan@xxxxxxxxxxxx
Reported-by: Derek Will <derekrobertwill@xxxxxxxxx>
Suggested-by: Derek Will <derekrobertwill@xxxxxxxxx>
Tested-by: Derek Will <derekrobertwill@xxxxxxxxx>
Signed-off-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/can/isotp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/can/isotp.c b/net/can/isotp.c
index ad61342d2e16..a95d171b3a64 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1009,7 +1009,7 @@ static int isotp_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
 	int noblock = flags & MSG_DONTWAIT;
 	int ret = 0;
 
-	if (flags & ~(MSG_DONTWAIT | MSG_TRUNC))
+	if (flags & ~(MSG_DONTWAIT | MSG_TRUNC | MSG_PEEK))
 		return -EINVAL;
 
 	if (!so->bound)
-- 
2.34.1