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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Flavio Leitner <fbl@redhat.com>,
        Hangbin Liu <liuhangbin@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 21/86] net/packet: fix packet_sock xmit return value checking
Date:   Tue, 26 Apr 2022 10:20:49 +0200
Message-Id: <20220426081741.823703703@linuxfoundation.org>
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From: Hangbin Liu <liuhangbin@gmail.com>

[ Upstream commit 29e8e659f984be00d75ec5fef4e37c88def72712 ]

packet_sock xmit could be dev_queue_xmit, which also returns negative
errors. So only checking positive errors is not enough, or userspace
sendmsg may return success while packet is not send out.

Move the net_xmit_errno() assignment in the braces as checkpatch.pl said
do not use assignment in if condition.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/packet/af_packet.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index d0c95d7dd292..5ee600d108a0 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2817,8 +2817,9 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
 
 		status = TP_STATUS_SEND_REQUEST;
 		err = po->xmit(skb);
-		if (unlikely(err > 0)) {
-			err = net_xmit_errno(err);
+		if (unlikely(err != 0)) {
+			if (err > 0)
+				err = net_xmit_errno(err);
 			if (err && __packet_get_status(po, ph) ==
 				   TP_STATUS_AVAILABLE) {
 				/* skb was destructed already */
@@ -3019,8 +3020,12 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 		skb->no_fcs = 1;
 
 	err = po->xmit(skb);
-	if (err > 0 && (err = net_xmit_errno(err)) != 0)
-		goto out_unlock;
+	if (unlikely(err != 0)) {
+		if (err > 0)
+			err = net_xmit_errno(err);
+		if (err)
+			goto out_unlock;
+	}
 
 	dev_put(dev);
 
-- 
2.35.1