From: Yan Zhai yan@cloudflare.com
commit 876e8ca8366735a604bac86ff7e2732fc9d85d2d upstream.
Commit 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.") introduced UDP listifyed GRO. The segmentation relies on frag_list being untouched when passing through the network stack. This assumption can be broken sometimes, where frag_list itself gets pulled into linear area, leaving frag_list being NULL. When this happens it can trigger following NULL pointer dereference, and panic the kernel. Reverse the test condition should fix it.
[19185.577801][ C1] BUG: kernel NULL pointer dereference, address: ... [19185.663775][ C1] RIP: 0010:skb_segment_list+0x1cc/0x390 ... [19185.834644][ C1] Call Trace: [19185.841730][ C1] <TASK> [19185.848563][ C1] __udp_gso_segment+0x33e/0x510 [19185.857370][ C1] inet_gso_segment+0x15b/0x3e0 [19185.866059][ C1] skb_mac_gso_segment+0x97/0x110 [19185.874939][ C1] __skb_gso_segment+0xb2/0x160 [19185.883646][ C1] udp_queue_rcv_skb+0xc3/0x1d0 [19185.892319][ C1] udp_unicast_rcv_skb+0x75/0x90 [19185.900979][ C1] ip_protocol_deliver_rcu+0xd2/0x200 [19185.910003][ C1] ip_local_deliver_finish+0x44/0x60 [19185.918757][ C1] __netif_receive_skb_one_core+0x8b/0xa0 [19185.927834][ C1] process_backlog+0x88/0x130 [19185.935840][ C1] __napi_poll+0x27/0x150 [19185.943447][ C1] net_rx_action+0x27e/0x5f0 [19185.951331][ C1] ? mlx5_cq_tasklet_cb+0x70/0x160 [mlx5_core] [19185.960848][ C1] __do_softirq+0xbc/0x25d [19185.968607][ C1] irq_exit_rcu+0x83/0xb0 [19185.976247][ C1] common_interrupt+0x43/0xa0 [19185.984235][ C1] asm_common_interrupt+0x22/0x40 ... [19186.094106][ C1] </TASK>
Fixes: 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.") Suggested-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: Willem de Bruijn willemb@google.com Signed-off-by: Yan Zhai yan@cloudflare.com Acked-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/r/Y9gt5EUizK1UImEP@debian Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/skbuff.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
--- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3884,7 +3884,7 @@ struct sk_buff *skb_segment_list(struct
skb_shinfo(skb)->frag_list = NULL;
- do { + while (list_skb) { nskb = list_skb; list_skb = list_skb->next;
@@ -3930,8 +3930,7 @@ struct sk_buff *skb_segment_list(struct if (skb_needs_linearize(nskb, features) && __skb_linearize(nskb)) goto err_linearize; - - } while (list_skb); + }
skb->truesize = skb->truesize - delta_truesize; skb->data_len = skb->data_len - delta_len;