kernel: ipv6: ip6_fragment: fix headroom tests and skb leak
authorFelix Fietkau <nbd@openwrt.org>
Thu, 17 Sep 2015 15:38:46 +0000 (15:38 +0000)
committerFelix Fietkau <nbd@openwrt.org>
Thu, 17 Sep 2015 15:38:46 +0000 (15:38 +0000)
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
SVN-Revision: 46992

target/linux/generic/patches-3.18/082-ipv6-ip6_fragment-fix-headroom-tests-and-skb-leak.patch [new file with mode: 0644]
target/linux/generic/patches-3.18/667-ipv6-Fixed-source-specific-default-route-handling.patch
target/linux/generic/patches-4.1/080-ipv6-ip6_fragment-fix-headroom-tests-and-skb-leak.patch [new file with mode: 0644]

diff --git a/target/linux/generic/patches-3.18/082-ipv6-ip6_fragment-fix-headroom-tests-and-skb-leak.patch b/target/linux/generic/patches-3.18/082-ipv6-ip6_fragment-fix-headroom-tests-and-skb-leak.patch
new file mode 100644 (file)
index 0000000..7c833c4
--- /dev/null
@@ -0,0 +1,101 @@
+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
+@@ -594,20 +594,22 @@ 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? */
+@@ -624,8 +626,6 @@ 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;
+@@ -633,8 +633,11 @@ 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));
+@@ -732,7 +735,6 @@ slow_path:
+        */
+       *prevhdr = NEXTHDR_FRAGMENT;
+-      hroom = LL_RESERVED_SPACE(rt->dst.dev);
+       troom = rt->dst.dev->needed_tailroom;
+       /*
index f67ef47..d02e085 100644 (file)
@@ -26,7 +26,7 @@ Signed-off-by: David S. Miller <davem@davemloft.net>
 
 --- a/net/ipv6/ip6_output.c
 +++ b/net/ipv6/ip6_output.c
-@@ -898,21 +898,45 @@ static int ip6_dst_lookup_tail(struct so
+@@ -900,21 +900,45 @@ static int ip6_dst_lookup_tail(struct so
  #endif
        int err;
  
diff --git a/target/linux/generic/patches-4.1/080-ipv6-ip6_fragment-fix-headroom-tests-and-skb-leak.patch b/target/linux/generic/patches-4.1/080-ipv6-ip6_fragment-fix-headroom-tests-and-skb-leak.patch
new file mode 100644 (file)
index 0000000..7de8987
--- /dev/null
@@ -0,0 +1,101 @@
+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
+@@ -584,20 +584,22 @@ int ip6_fragment(struct sock *sk, struct
+       }
+       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? */
+@@ -614,8 +616,6 @@ int ip6_fragment(struct sock *sk, struct
+               err = 0;
+               offset = 0;
+-              frag = skb_shinfo(skb)->frag_list;
+-              skb_frag_list_init(skb);
+               /* BUILD HEADER */
+               *prevhdr = NEXTHDR_FRAGMENT;
+@@ -623,8 +623,11 @@ int ip6_fragment(struct sock *sk, struct
+               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));
+@@ -722,7 +725,6 @@ slow_path:
+        */
+       *prevhdr = NEXTHDR_FRAGMENT;
+-      hroom = LL_RESERVED_SPACE(rt->dst.dev);
+       troom = rt->dst.dev->needed_tailroom;
+       /*