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authorYonghong Song <yhs@fb.com>2018-03-22 00:31:03 +0100
committerDavid S. Miller <davem@davemloft.net>2018-03-25 22:46:04 +0200
commit13acc94eff122b260a387d68668bf9d670738e6a (patch)
treee54fdfe797f6c0f2f0fe45e8fd19641b5bd541dc /net/core
parentMerge branch '10GbE' of git://git.kernel.org/pub/scm/linux/kernel/git/jkirshe... (diff)
downloadlinux-13acc94eff122b260a387d68668bf9d670738e6a.tar.xz
linux-13acc94eff122b260a387d68668bf9d670738e6a.zip
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>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/skbuff.c27
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);