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authorFlorian Westphal <fw@strlen.de>2015-09-16 17:26:14 +0200
committerDavid S. Miller <davem@davemloft.net>2015-09-17 21:36:15 -0700
commit1d325d217c7f190a42fb620ead20bb240fc16af0 (patch)
treee22033623847be89a17e35e046f0e57953cc75a3 /net/ipv6/ip6_output.c
parentce816eb064c82ab96276969971a561db78e66164 (diff)
downloadlinux-sh-1d325d217c7f190a42fb620ead20bb240fc16af0.tar.gz
ipv6: ip6_fragment: fix headroom tests and skb leak
David Woodhouse reports skb_under_panic when we try to push ethernet header to fragmented ipv6 skbs: skbuff: skb_under_panic: text:c1277f1e len:1294 put:14 head:dec98000 data:dec97ffc tail:0xdec9850a end:0xdec98f40 dev:br-lan [..] ip6_finish_output2+0x196/0x4da David further debugged this: [..] offending fragments were arriving here with skb_headroom(skb)==10. Which is reasonable, being the Solos ADSL card's header of 8 bytes followed by 2 bytes of PPP frame type. The problem is that if netfilter ipv6 defragmentation is used, skb_cow() in ip6_forward will only see reassembled skb. Therefore, headroom is overestimated by 8 bytes (we pulled fragment header) and we don't check the skbs in the frag_list either. We can't do these checks in netfilter defrag since outdev isn't known yet. Furthermore, existing tests in ip6_fragment did not consider the fragment or ipv6 header size when checking headroom of the fraglist skbs. While at it, also fix a skb leak on memory allocation -- ip6_fragment must consume the skb. I tested this e1000 driver hacked to not allocate additional headroom (we end up in slowpath, since LL_RESERVED_SPACE is 16). If 2 bytes of headroom are allocated, fastpath is taken (14 byte ethernet header was pulled, so 16 byte headroom available in all fragments). Reported-by: David Woodhouse <dwmw2@infradead.org> Diagnosed-by: David Woodhouse <dwmw2@infradead.org> Signed-off-by: Florian Westphal <fw@strlen.de> Tested-by: David Woodhouse <David.Woodhouse@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/ip6_output.c')
-rw-r--r--net/ipv6/ip6_output.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 26ea47930740..92b1aa38f121 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -586,20 +586,22 @@ int ip6_fragment(struct sock *sk, struct sk_buff *skb,
frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr,
&ipv6_hdr(skb)->saddr);
+ hroom = LL_RESERVED_SPACE(rt->dst.dev);
if (skb_has_frag_list(skb)) {
int first_len = skb_pagelen(skb);
struct sk_buff *frag2;
if (first_len - hlen > mtu ||
((first_len - hlen) & 7) ||
- skb_cloned(skb))
+ skb_cloned(skb) ||
+ skb_headroom(skb) < (hroom + sizeof(struct frag_hdr)))
goto slow_path;
skb_walk_frags(skb, frag) {
/* Correct geometry. */
if (frag->len > mtu ||
((frag->len & 7) && frag->next) ||
- skb_headroom(frag) < hlen)
+ skb_headroom(frag) < (hlen + hroom + sizeof(struct frag_hdr)))
goto slow_path_clean;
/* Partially cloned skb? */
@@ -616,8 +618,6 @@ int ip6_fragment(struct sock *sk, struct sk_buff *skb,
err = 0;
offset = 0;
- frag = skb_shinfo(skb)->frag_list;
- skb_frag_list_init(skb);
/* BUILD HEADER */
*prevhdr = NEXTHDR_FRAGMENT;
@@ -625,8 +625,11 @@ int ip6_fragment(struct sock *sk, struct sk_buff *skb,
if (!tmp_hdr) {
IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
IPSTATS_MIB_FRAGFAILS);
- return -ENOMEM;
+ err = -ENOMEM;
+ goto fail;
}
+ frag = skb_shinfo(skb)->frag_list;
+ skb_frag_list_init(skb);
__skb_pull(skb, hlen);
fh = (struct frag_hdr *)__skb_push(skb, sizeof(struct frag_hdr));
@@ -723,7 +726,6 @@ slow_path:
*/
*prevhdr = NEXTHDR_FRAGMENT;
- hroom = LL_RESERVED_SPACE(rt->dst.dev);
troom = rt->dst.dev->needed_tailroom;
/*