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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hallo Shaunak, many thanks for your patch. But there's already a fix awaiting upstream: https://lore.kernel.org/linux-can/20260917123716.63116-1-ndaugoing@gmail.com/ Best regards, Oliver On 18.09.26 17:16, Shaunak Datar wrote: > __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)