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Tue, 29 Sep 2026 21:07:02 +0000 (UTC) From: Marc Kleine-Budde To: netdev@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, linux-can@vger.kernel.org, kernel@pengutronix.de, zjamg , stable@vger.kernel.org, Oliver Hartkopp , Quchaosheng , Shaunak Datar , Marc Kleine-Budde Subject: [PATCH net 02/16] can: dev: init_can_skb(): restore skb header initialization Date: Tue, 29 Sep 2026 22:43:52 +0200 Message-ID: <20260929210700.1183036-3-mkl@pengutronix.de> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260929210700.1183036-1-mkl@pengutronix.de> References: <20260929210700.1183036-1-mkl@pengutronix.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: zjamg Commit 9f10374bb024 ("can: remove private CAN skb headroom infrastructure") removed the skb_reset_mac_header()/skb_reset_network_header()/ skb_reset_transport_header() calls from init_can_skb(). As a result, RX skbs from alloc_can_skb() and friends again carry mac_header = 0xFFFF. When such an skb reaches packet_rcv_spkt() (SOCK_PACKET), the push length calculation overflows and triggers skb_under_panic -> kernel BUG -> full machine panic. The same issue was originally reported in 2014 on linux-can and fixed by commit 969439016d2c ("can: add missing initialisations in CAN related skbuffs"). packet_rcv_spkt() itself has never been hardened: only packet_rcv() and tpacket_rcv() gained dev_has_header() checks in commit d549699048b4 ("net/packet: fix packet receive on L3 devices without visible hard header"). Fixes: 9f10374bb024 ("can: remove private CAN skb headroom infrastructure") Cc: stable@vger.kernel.org Reviewed-by: Oliver Hartkopp Acked-by: Oliver Hartkopp Signed-off-by: zjamg Tested-by: Quchaosheng Link: https://patch.msgid.link/20260917123716.63116-1-ndaugoing@gmail.com Reported-by: Shaunak Datar Closes: https://lore.kernel.org/all/20260918151606.765490-1-shaunakkdatar@gmail.com Signed-off-by: Marc Kleine-Budde --- drivers/net/can/dev/skb.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c index 4f7a189de265..bc0787535b52 100644 --- a/drivers/net/can/dev/skb.c +++ b/drivers/net/can/dev/skb.c @@ -211,6 +211,10 @@ static void init_can_skb(struct sk_buff *skb) { skb->pkt_type = PACKET_BROADCAST; skb->ip_summed = CHECKSUM_UNNECESSARY; + + skb_reset_mac_header(skb); + skb_reset_network_header(skb); + skb_reset_transport_header(skb); } struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf) -- 2.53.0