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authorEric Dumazet <edumazet@google.com>2017-05-19 14:17:48 -0700
committerBen Hutchings <ben@decadent.org.uk>2017-06-05 21:13:57 +0100
commite5238fca9694d61861096d5fb80685c9f6581555 (patch)
treebdf8fd5b753396104c323008d4ad27ffba4d7c2e
parent0767192a2c4ac9145a7e8fb00370963bc145a920 (diff)
ipv6: fix out of bound writes in __ip6_append_data()
commit 232cd35d0804cc241eb887bb8d4d9b3b9881c64a upstream. 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> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
-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 81a780354f31..4ce3e3f32802 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1416,6 +1416,11 @@ 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,
@@ -1467,13 +1472,9 @@ 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;