The blamed commit changed the dsa_8021q_rcv() calling convention to
accept pre-populated source_port and switch_id arguments. If those are
not available, as in the case of tag_ocelot_8021q, the arguments must be
pre-initialized with -1.

Due to the bug of passing uninitialized arguments in tag_ocelot_8021q,
dsa_8021q_rcv() does not detect that it needs to populate the
source_port and switch_id, and this makes dsa_conduit_find_user() fail,
which leads to packet loss on reception.

Fixes: dcfe7673787b ("net: dsa: tag_sja1105: absorb logic for not overwriting precise info into dsa_8021q_rcv()")
Signed-off-by: Robert Hodaszi <robert.hodaszi@digi.com>
---
Cc: stable@vger.kernel.org
---
 net/dsa/tag_ocelot_8021q.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/dsa/tag_ocelot_8021q.c b/net/dsa/tag_ocelot_8021q.c
index 8e8b1bef6af6..11ea8cfd6266 100644
--- a/net/dsa/tag_ocelot_8021q.c
+++ b/net/dsa/tag_ocelot_8021q.c
@@ -79,7 +79,7 @@ static struct sk_buff *ocelot_xmit(struct sk_buff *skb,
 static struct sk_buff *ocelot_rcv(struct sk_buff *skb,
 				  struct net_device *netdev)
 {
-	int src_port, switch_id;
+	int src_port = -1, switch_id = -1;
 
 	dsa_8021q_rcv(skb, &src_port, &switch_id, NULL, NULL);
 
-- 
2.43.0

On Wed, Dec 11, 2024 at 03:47:41PM +0100, Robert Hodaszi wrote:
> The blamed commit changed the dsa_8021q_rcv() calling convention to
> accept pre-populated source_port and switch_id arguments. If those are
> not available, as in the case of tag_ocelot_8021q, the arguments must be
> pre-initialized with -1.
> 
> Due to the bug of passing uninitialized arguments in tag_ocelot_8021q,
> dsa_8021q_rcv() does not detect that it needs to populate the
> source_port and switch_id, and this makes dsa_conduit_find_user() fail,
> which leads to packet loss on reception.
> 
> Fixes: dcfe7673787b ("net: dsa: tag_sja1105: absorb logic for not overwriting precise info into dsa_8021q_rcv()")
> Signed-off-by: Robert Hodaszi <robert.hodaszi@digi.com>
> ---

Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>