102 lines
3.1 KiB
Diff
102 lines
3.1 KiB
Diff
From: Florian Westphal <fw@strlen.de>
|
|
Date: Thu, 17 Sep 2015 11:24:48 +0100
|
|
Subject: [PATCH] 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>
|
|
Closes 20532
|
|
---
|
|
|
|
--- a/net/ipv6/ip6_output.c
|
|
+++ b/net/ipv6/ip6_output.c
|
|
@@ -597,20 +597,22 @@ int ip6_fragment(struct sk_buff *skb, in
|
|
}
|
|
mtu -= hlen + sizeof(struct frag_hdr);
|
|
|
|
+ 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? */
|
|
@@ -627,8 +629,6 @@ int ip6_fragment(struct sk_buff *skb, in
|
|
|
|
err = 0;
|
|
offset = 0;
|
|
- frag = skb_shinfo(skb)->frag_list;
|
|
- skb_frag_list_init(skb);
|
|
/* BUILD HEADER */
|
|
|
|
*prevhdr = NEXTHDR_FRAGMENT;
|
|
@@ -636,8 +636,11 @@ int ip6_fragment(struct sk_buff *skb, in
|
|
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));
|
|
@@ -735,7 +738,6 @@ slow_path:
|
|
*/
|
|
|
|
*prevhdr = NEXTHDR_FRAGMENT;
|
|
- hroom = LL_RESERVED_SPACE(rt->dst.dev);
|
|
troom = rt->dst.dev->needed_tailroom;
|
|
|
|
/*
|