Commit 38f02f2c authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman

ipv6: fix out of bound writes in __ip6_append_data()


[ Upstream commit 232cd35d ]

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: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Tested-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Reported-by: <idaifish@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3a854210
......@@ -1432,6 +1432,11 @@ static int __ip6_append_data(struct sock *sk,
*/
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,
......@@ -1481,13 +1486,9 @@ static int __ip6_append_data(struct sock *sk,
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;
......
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