| Message ID | 20230511125440.1177848-1-dongchenchen2@huawei.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | c83b49383b595be50647f0c764a48c78b5f3c4f8 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v4] net: nsh: Use correct mac_offset to unwind gso skb in nsh_gso_segment() | expand |
Hello: This patch was applied to netdev/net.git (main) by David S. Miller <davem@davemloft.net>: On Thu, 11 May 2023 20:54:40 +0800 you wrote: > As the call trace shows, skb_panic was caused by wrong skb->mac_header > in nsh_gso_segment(): > > invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI > CPU: 3 PID: 2737 Comm: syz Not tainted 6.3.0-next-20230505 #1 > RIP: 0010:skb_panic+0xda/0xe0 > call Trace: > skb_push+0x91/0xa0 > nsh_gso_segment+0x4f3/0x570 > skb_mac_gso_segment+0x19e/0x270 > __skb_gso_segment+0x1e8/0x3c0 > validate_xmit_skb+0x452/0x890 > validate_xmit_skb_list+0x99/0xd0 > sch_direct_xmit+0x294/0x7c0 > __dev_queue_xmit+0x16f0/0x1d70 > packet_xmit+0x185/0x210 > packet_snd+0xc15/0x1170 > packet_sendmsg+0x7b/0xa0 > sock_sendmsg+0x14f/0x160 > > [...] Here is the summary with links: - [net,v4] net: nsh: Use correct mac_offset to unwind gso skb in nsh_gso_segment() https://git.kernel.org/netdev/net/c/c83b49383b59 You are awesome, thank you!
diff --git a/net/nsh/nsh.c b/net/nsh/nsh.c index e9ca007718b7..0f23e5e8e03e 100644 --- a/net/nsh/nsh.c +++ b/net/nsh/nsh.c @@ -77,13 +77,12 @@ static struct sk_buff *nsh_gso_segment(struct sk_buff *skb, netdev_features_t features) { struct sk_buff *segs = ERR_PTR(-EINVAL); + u16 mac_offset = skb->mac_header; unsigned int nsh_len, mac_len; __be16 proto; - int nhoff; skb_reset_network_header(skb); - nhoff = skb->network_header - skb->mac_header; mac_len = skb->mac_len; if (unlikely(!pskb_may_pull(skb, NSH_BASE_HDR_LEN))) @@ -108,15 +107,14 @@ static struct sk_buff *nsh_gso_segment(struct sk_buff *skb, segs = skb_mac_gso_segment(skb, features); if (IS_ERR_OR_NULL(segs)) { skb_gso_error_unwind(skb, htons(ETH_P_NSH), nsh_len, - skb->network_header - nhoff, - mac_len); + mac_offset, mac_len); goto out; } for (skb = segs; skb; skb = skb->next) { skb->protocol = htons(ETH_P_NSH); __skb_push(skb, nsh_len); - skb_set_mac_header(skb, -nhoff); + skb->mac_header = mac_offset; skb->network_header = skb->mac_header + mac_len; skb->mac_len = mac_len; }
As the call trace shows, skb_panic was caused by wrong skb->mac_header in nsh_gso_segment(): invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 3 PID: 2737 Comm: syz Not tainted 6.3.0-next-20230505 #1 RIP: 0010:skb_panic+0xda/0xe0 call Trace: skb_push+0x91/0xa0 nsh_gso_segment+0x4f3/0x570 skb_mac_gso_segment+0x19e/0x270 __skb_gso_segment+0x1e8/0x3c0 validate_xmit_skb+0x452/0x890 validate_xmit_skb_list+0x99/0xd0 sch_direct_xmit+0x294/0x7c0 __dev_queue_xmit+0x16f0/0x1d70 packet_xmit+0x185/0x210 packet_snd+0xc15/0x1170 packet_sendmsg+0x7b/0xa0 sock_sendmsg+0x14f/0x160 The root cause is: nsh_gso_segment() use skb->network_header - nhoff to reset mac_header in skb_gso_error_unwind() if inner-layer protocol gso fails. However, skb->network_header may be reset by inner-layer protocol gso function e.g. mpls_gso_segment. skb->mac_header reset by the inaccurate network_header will be larger than skb headroom. nsh_gso_segment nhoff = skb->network_header - skb->mac_header; __skb_pull(skb,nsh_len) skb_mac_gso_segment mpls_gso_segment skb_reset_network_header(skb);//skb->network_header+=nsh_len return -EINVAL; skb_gso_error_unwind skb_push(skb, nsh_len); skb->mac_header = skb->network_header - nhoff; // skb->mac_header > skb->headroom, cause skb_push panic Use correct mac_offset to restore mac_header and get rid of nhoff. Fixes: c411ed854584 ("nsh: add GSO support") Reported-by: syzbot+632b5d9964208bfef8c0@syzkaller.appspotmail.com Suggested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- v2: - Use skb->mac_header not skb->network_header-nhoff for mac_offset. v3: - 'net' is noted in the subject. - arrange local variable following reverse xmas tree order v4: - get rid of nhoff --- net/nsh/nsh.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)