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Fri, 18 Sep 2026 08:16:30 -0700 (PDT) Received: from shaunak ([103.48.102.247]) by smtp.gmail.com with ESMTPSA id 00721157ae682-897ea659c06sm5814157b3.49.2026.09.18.08.16.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2026 08:16:29 -0700 (PDT) From: Shaunak Datar To: mkl@pengutronix.de, mailhol@kernel.org Cc: pabeni@redhat.com, socketcan@hartkopp.net, linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, Shaunak Datar , syzbot+1aae11dc8d42ec1a87ec@syzkaller.appspotmail.com Subject: [PATCH] can: dev: fix missing skb header initialization in init_can_skb Date: Fri, 18 Sep 2026 20:46:06 +0530 Message-ID: <20260918151606.765490-1-shaunakkdatar@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-can@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit __alloc_skb() sets skb->mac_header to (typeof(skb->mac_header))~0U via __finalize_skb_around(). skb_reset_mac_len() checks if the value has been updated via the skb_mac_header_was_set() and fires DEBUG_NET_WARN_ON_ONCE(1) if not. init_can_skb() previously included three header reset calls: - skb_reset_mac_header(skb) - skb_reset_network_header(skb) - skb_reset_transport_header(skb) Commit 9f10374bb024 ("can: remove private CAN skb headroom infrastructure") dropped these calls which leads to the skb->mac_header retaining the original value. Restore the three missing calls in the init_can_skb(). Fixes: 9f10374bb024 ("can: remove private CAN skb headroom infrastructure") Reported-by: syzbot+1aae11dc8d42ec1a87ec@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1aae11dc8d42ec1a87ec Signed-off-by: Shaunak Datar --- drivers/net/can/dev/skb.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c index 95fcdc1026f8..9cbddc1edd41 100644 --- a/drivers/net/can/dev/skb.c +++ b/drivers/net/can/dev/skb.c @@ -210,6 +210,9 @@ 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