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authorEric Dumazet <edumazet@google.com>2017-05-20 00:17:48 +0300
committerDavid S. Miller <davem@davemloft.net>2017-05-22 18:47:44 +0300
commit232cd35d0804cc241eb887bb8d4d9b3b9881c64a (patch)
treec4c562db86e7f3c60775748ce696efc2a0b8b54b /net
parent6d18c732b95c0a9d35e9f978b4438bba15412284 (diff)
downloadlinux-232cd35d0804cc241eb887bb8d4d9b3b9881c64a.tar.xz
ipv6: fix out of bound writes in __ip6_append_data()
Andrey Konovalov and idaifish@gmail.com reported crashes caused by one skb shared_info being overwritten from __ip6_append_data() Andrey program lead to following state : copy -4200 datalen 2000 fraglen 2040 maxfraglen 2040 alloclen 2048 transhdrlen 0 offset 0 fraggap 6200 The skb_copy_and_csum_bits(skb_prev, maxfraglen, data + transhdrlen, fraggap, 0); is overwriting skb->head and skb_shared_info Since we apparently detect this rare condition too late, move the code earlier to even avoid allocating skb and risking crashes. Once again, many thanks to Andrey and syzkaller team. Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Andrey Konovalov <andreyknvl@google.com> Tested-by: Andrey Konovalov <andreyknvl@google.com> Reported-by: <idaifish@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv6/ip6_output.c15
1 files changed, 8 insertions, 7 deletions
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index d4a31becbd25..bf8a58a1c32d 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1466,6 +1466,11 @@ alloc_new_skb:
*/
alloclen += sizeof(struct frag_hdr);
+ copy = datalen - transhdrlen - fraggap;
+ if (copy < 0) {
+ err = -EINVAL;
+ goto error;
+ }
if (transhdrlen) {
skb = sock_alloc_send_skb(sk,
alloclen + hh_len,
@@ -1515,13 +1520,9 @@ alloc_new_skb:
data += fraggap;
pskb_trim_unique(skb_prev, maxfraglen);
}
- copy = datalen - transhdrlen - fraggap;
-
- if (copy < 0) {
- err = -EINVAL;
- kfree_skb(skb);
- goto error;
- } else if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
+ if (copy > 0 &&
+ getfrag(from, data + transhdrlen, offset,
+ copy, fraggap, skb) < 0) {
err = -EFAULT;
kfree_skb(skb);
goto error;