From: Subash Abhinov Kasiviswanathan quic_subashab@quicinc.com
[ Upstream commit 2d7afdcbc9d32423f177ee12b7c93783aea338fb ]
Extending the tail can have some unexpected side effects if a program uses a helper like BPF_FUNC_skb_pull_data to read partial content beyond the head skb headlen when all the skbs in the gso frag_list are linear with no head_frag -
kernel BUG at net/core/skbuff.c:4219! pc : skb_segment+0xcf4/0xd2c lr : skb_segment+0x63c/0xd2c Call trace: skb_segment+0xcf4/0xd2c __udp_gso_segment+0xa4/0x544 udp4_ufo_fragment+0x184/0x1c0 inet_gso_segment+0x16c/0x3a4 skb_mac_gso_segment+0xd4/0x1b0 __skb_gso_segment+0xcc/0x12c udp_rcv_segment+0x54/0x16c udp_queue_rcv_skb+0x78/0x144 udp_unicast_rcv_skb+0x8c/0xa4 __udp4_lib_rcv+0x490/0x68c udp_rcv+0x20/0x30 ip_protocol_deliver_rcu+0x1b0/0x33c ip_local_deliver+0xd8/0x1f0 ip_rcv+0x98/0x1a4 deliver_ptype_list_skb+0x98/0x1ec __netif_receive_skb_core+0x978/0xc60
Fix this by marking these skbs as GSO_DODGY so segmentation can handle the tail updates accordingly.
Fixes: 3dcbdb134f32 ("net: gso: Fix skb_segment splat when splitting gso_size mangled skb having linear-headed frag_list") Signed-off-by: Sean Tranchetti quic_stranche@quicinc.com Signed-off-by: Subash Abhinov Kasiviswanathan quic_subashab@quicinc.com Reviewed-by: Alexander Duyck alexanderduyck@fb.com Link: https://lore.kernel.org/r/1671084718-24796-1-git-send-email-quic_subashab@qu... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/skbuff.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 4178fc28c277..7f501dff4501 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1953,6 +1953,9 @@ void *__pskb_pull_tail(struct sk_buff *skb, int delta) insp = list; } else { /* Eaten partially. */ + if (skb_is_gso(skb) && !list->head_frag && + skb_headlen(list)) + skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
if (skb_shared(list)) { /* Sucks! We need to fork list. :-( */