From: Asim Viladi Oglu Manizada Date: Wed, 22 Jul 2026 09:38:43 +0000 (+0000) Subject: pppoe: reload header pointer after dev_hard_header() X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e9c238f6fe42fb1b4dba3a578277de32cb487937;p=thirdparty%2Fkernel%2Flinux.git pppoe: reload header pointer after dev_hard_header() pppoe_sendmsg() saves a pointer to the PPPoE header before calling dev_hard_header(). Device header callbacks are allowed to reallocate the skb head, invalidating pointers into it. This can happen when a send is blocked in copy_from_user() while the first non-Ethernet port is added to an empty team device. The team's delegated GRE header callback then expands the skb head. PPPoE subsequently writes six bytes through the stale pointer into the freed head. Reload the PPPoE header through the skb's network-header offset after device header creation. pskb_expand_head() updates that offset when it relocates the head. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Asim Viladi Oglu Manizada Reviewed-by: Vadim Fedorenko Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260722093814.3017176-1-manizada@pm.me Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c index 4a018acb5262..6874a1a8edaf 100644 --- a/drivers/net/ppp/pppoe.c +++ b/drivers/net/ppp/pppoe.c @@ -825,6 +825,7 @@ static int pppoe_sendmsg(struct socket *sock, struct msghdr *m, dev_hard_header(skb, dev, ETH_P_PPP_SES, po->pppoe_pa.remote, NULL, total_len); + ph = pppoe_hdr(skb); memcpy(ph, &hdr, sizeof(struct pppoe_hdr)); ph->length = htons(total_len);