| Message ID | 20230509021924.554576-1-dongchenchen2@huawei.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [next,v2] net: nsh: Use correct mac_offset to unwind gso skb in nsh_gso_segment() | expand |
On Tue, May 09, 2023 at 10:19:24AM +0800, Dong Chenchen 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 > > 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 to fix it. > > Fixes: c411ed854584 ("nsh: add GSO support") > Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> nit: As this is a fix it should probably be targeted at 'net' (as opposed to 'net-next'). This should be noted in the subject. Subject: [PATCH net v2]... > --- > v2: > - Use skb->mac_header not skb->network_header-nhoff for mac_offset. > --- > net/nsh/nsh.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/net/nsh/nsh.c b/net/nsh/nsh.c > index e9ca007718b7..7eb536a9677f 100644 > --- a/net/nsh/nsh.c > +++ b/net/nsh/nsh.c > @@ -78,6 +78,7 @@ static struct sk_buff *nsh_gso_segment(struct sk_buff *skb, > { > struct sk_buff *segs = ERR_PTR(-EINVAL); > unsigned int nsh_len, mac_len; > + u16 mac_offset = skb->mac_header; nit: It is generally preferred to arrange local variable in networking code from shortest line to longest - reverse xmas tree order. This can be verified using. https://github.com/ecree-solarflare/xmastree/blob/master/README > __be16 proto; > int nhoff; > > @@ -108,8 +109,7 @@ 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; > } > > -- > 2.25.1 > >
diff --git a/net/nsh/nsh.c b/net/nsh/nsh.c index e9ca007718b7..7eb536a9677f 100644 --- a/net/nsh/nsh.c +++ b/net/nsh/nsh.c @@ -78,6 +78,7 @@ static struct sk_buff *nsh_gso_segment(struct sk_buff *skb, { struct sk_buff *segs = ERR_PTR(-EINVAL); unsigned int nsh_len, mac_len; + u16 mac_offset = skb->mac_header; __be16 proto; int nhoff; @@ -108,8 +109,7 @@ 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; }
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 to fix it. Fixes: c411ed854584 ("nsh: add GSO support") Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- v2: - Use skb->mac_header not skb->network_header-nhoff for mac_offset. --- net/nsh/nsh.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)