[PATCH 6.18 193/395] bridge: check llc_mac_hdr_init() return value in br_send_bpdu()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit ac704ff08e511c87643799c385f55ecd69b85e03 ]

If llc_mac_hdr_init() fails (for instance if the port device type does
not support LLC or dev_hard_header() fails), br_send_bpdu() should drop
the skb instead of resetting the mac header to the LLC payload and
transmitting a malformed frame.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Closes: https://lore.kernel.org/netdev/179022851638.2160803.1808206741379444999@kernel.org/
Cc: Nikolay Aleksandrov <razor@blackwall.org>
Cc: Ido Schimmel <idosch@nvidia.com>
Cc: bridge@lists.linux.dev
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260924082951.1599377-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/bridge/br_stp_bpdu.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/bridge/br_stp_bpdu.c b/net/bridge/br_stp_bpdu.c
index 7895489ac6fe7..e44e448b1157b 100644
--- a/net/bridge/br_stp_bpdu.c
+++ b/net/bridge/br_stp_bpdu.c
@@ -52,7 +52,10 @@ static void br_send_bpdu(struct net_bridge_port *p,
 			    LLC_SAP_BSPAN, LLC_PDU_CMD);
 	llc_pdu_init_as_ui_cmd(skb);
 
-	llc_mac_hdr_init(skb, p->dev->dev_addr, p->br->group_addr);
+	if (llc_mac_hdr_init(skb, p->dev->dev_addr, p->br->group_addr)) {
+		kfree_skb(skb);
+		return;
+	}
 
 	skb_reset_mac_header(skb);
 
-- 
2.53.0