diff options
| author | Yonghong Song <yhs@fb.com> | 2018-03-21 16:31:03 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-03-25 16:46:04 -0400 |
| commit | 13acc94eff122b260a387d68668bf9d670738e6a (patch) | |
| tree | e54fdfe797f6c0f2f0fe45e8fd19641b5bd541dc | |
| parent | 0374016579d0ef5d86655e48645ccc05678e0cf5 (diff) | |
net: permit skb_segment on head_frag frag_list skb
One of our in-house projects, bpf-based NAT, hits a kernel BUG_ON at
function skb_segment(), line 3667. The bpf program attaches to
clsact ingress, calls bpf_skb_change_proto to change protocol
from ipv4 to ipv6 or from ipv6 to ipv4, and then calls bpf_redirect
to send the changed packet out.
3472 struct sk_buff *skb_segment(struct sk_buff *head_skb,
3473 netdev_features_t features)
3474 {
3475 struct sk_buff *segs = NULL;
3476 struct sk_buff *tail = NULL;
...
3665 while (pos < offset + len) {
3666 if (i >= nfrags) {
3667 BUG_ON(skb_headlen(list_skb));
3668
3669 i = 0;
3670 nfrags = skb_shinfo(list_skb)->nr_frags;
3671 frag = skb_shinfo(list_skb)->frags;
3672 frag_skb = list_skb;
...
call stack:
...
#1 [ffff883ffef03558] __crash_kexec at ffffffff8110c525
#2 [ffff883ffef03620] crash_kexec at ffffffff8110d5cc
#3 [ffff883ffef03640] oops_end at ffffffff8101d7e7
#4 [ffff883ffef03668] die at ffffffff8101deb2
#5 [ffff883ffef03698] do_trap at ffffffff8101a700
#6 [ffff883ffef036e8] do_error_trap at ffffffff8101abfe
#7 [ffff883ffef037a0] do_invalid_op at ffffffff8101acd0
#8 [ffff883ffef037b0] invalid_op at ffffffff81a00bab
[exception RIP: skb_segment+3044]
RIP: ffffffff817e4dd4 RSP: ffff883ffef03860 RFLAGS: 00010216
RAX: 0000000000002bf6 RBX: ffff883feb7aaa00 RCX: 0000000000000011
RDX: ffff883fb87910c0 RSI: 0000000000000011 RDI: ffff883feb7ab500
RBP: ffff883ffef03928 R8: 0000000000002ce2 R9: 00000000000027da
R10: 000001ea00000000 R11: 0000000000002d82 R12: ffff883f90a1ee80
R13: ffff883fb8791120 R14: ffff883feb7abc00 R15: 0000000000002ce2
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#9 [ffff883ffef03930] tcp_gso_segment at ffffffff818713e7
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/core/skbuff.c | 27 |
1 files changed, 22 insertions, 5 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 46cb22215ff4..b5c75d4fcf37 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3460,6 +3460,19 @@ void *skb_pull_rcsum(struct sk_buff *skb, unsigned int len) } EXPORT_SYMBOL_GPL(skb_pull_rcsum); +static inline skb_frag_t skb_head_frag_to_page_desc(struct sk_buff *frag_skb) +{ + skb_frag_t head_frag; + struct page *page; + + page = virt_to_head_page(frag_skb->head); + head_frag.page.p = page; + head_frag.page_offset = frag_skb->data - + (unsigned char *)page_address(page); + head_frag.size = skb_headlen(frag_skb); + return head_frag; +} + /** * skb_segment - Perform protocol segmentation on skb. * @head_skb: buffer to segment @@ -3664,15 +3677,19 @@ normal: while (pos < offset + len) { if (i >= nfrags) { - BUG_ON(skb_headlen(list_skb)); - i = 0; nfrags = skb_shinfo(list_skb)->nr_frags; frag = skb_shinfo(list_skb)->frags; frag_skb = list_skb; + if (!skb_headlen(list_skb)) { + BUG_ON(!nfrags); + } else { + BUG_ON(!list_skb->head_frag); - BUG_ON(!nfrags); - + /* to make room for head_frag. */ + i--; + frag--; + } if (skb_orphan_frags(frag_skb, GFP_ATOMIC) || skb_zerocopy_clone(nskb, frag_skb, GFP_ATOMIC)) @@ -3689,7 +3706,7 @@ normal: goto err; } - *nskb_frag = *frag; + *nskb_frag = (i < 0) ? skb_head_frag_to_page_desc(frag_skb) : *frag; __skb_frag_ref(nskb_frag); size = skb_frag_size(nskb_frag); |