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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a027ce61cfsm4277091a91.8.2026.09.19.14.52.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 14:52:37 -0700 (PDT) From: Hui Peng To: willemdebruijn.kernel@gmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] net/packet: zero-pad spkt_device and preserve sa.origlen across MSG_PEEK Date: Sat, 19 Sep 2026 21:52:37 +0000 Message-ID: <20260919215237.3470987-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Fix two issues in net/packet/af_packet.c: 1. In packet_rcv_spkt(), use strscpy_pad() instead of strscpy() when populating spkt->spkt_device so trailing bytes after dev->name's NUL terminator in the 14-byte buffer are zeroed. 2. In packet_recvmsg(), PACKET_SKB_CB(skb)->sa.origlen aliases sll->sll_family and sll->sll_protocol inside the union. Overwriting sll->sll_family and sll->sll_protocol in PACKET_SKB_CB(skb) directly clobbers sa.origlen for subsequent recvmsg(MSG_PEEK | MSG_TRUNC) calls on the same skb. Instead, write sll_family and sll_protocol into the destination msg->msg_name buffer after copying PACKET_SKB_CB(skb)->sa. Fixes: 2472d7613bd3 ("net: packet: use sockaddr_ll fields as storage for skb original length in recvmsg path") Assisted-by: LLM Signed-off-by: Hui Peng --- diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 50cae32ae269..15def2d16806 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1918,7 +1918,7 @@ static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev, */ spkt->spkt_family = dev->type; - strscpy(spkt->spkt_device, dev->name, sizeof(spkt->spkt_device)); + strscpy_pad(spkt->spkt_device, dev->name, sizeof(spkt->spkt_device)); spkt->spkt_protocol = skb->protocol; /* @@ -3510,15 +3510,8 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, if (err) goto out_free; - if (sock->type != SOCK_PACKET) { - struct sockaddr_ll *sll = &PACKET_SKB_CB(skb)->sa.ll; - - /* Original length was stored in sockaddr_ll fields */ + if (sock->type != SOCK_PACKET) origlen = PACKET_SKB_CB(skb)->sa.origlen; - sll->sll_family = AF_PACKET; - sll->sll_protocol = (sock->type == SOCK_DGRAM) ? - vlan_get_protocol_dgram(skb) : skb->protocol; - } sock_recv_cmsgs(msg, sk, skb); @@ -3552,6 +3545,13 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, msg->msg_namelen = copy_len; } memcpy(msg->msg_name, &PACKET_SKB_CB(skb)->sa, copy_len); + if (sock->type != SOCK_PACKET) { + struct sockaddr_ll *u_sll = msg->msg_name; + + u_sll->sll_family = AF_PACKET; + u_sll->sll_protocol = (sock->type == SOCK_DGRAM) ? + vlan_get_protocol_dgram(skb) : skb->protocol; + } } if (packet_sock_flag(pkt_sk(sk), PACKET_SOCK_AUXDATA)) {