Commit e553622c authored by Herbert Xu's avatar Herbert Xu Committed by Ben Hutchings

net: Fix skb_set_peeked use-after-free bug

commit a0a2a660 upstream.

The commit 738ac1eb ("net: Clone
skb before setting peeked flag") introduced a use-after-free bug
in skb_recv_datagram.  This is because skb_set_peeked may create
a new skb and free the existing one.  As it stands the caller will
continue to use the old freed skb.

This patch fixes it by making skb_set_peeked return the new skb
(or the old one if unchanged).

Fixes: 738ac1eb ("net: Clone skb before setting peeked flag")
Reported-by: default avatarBrenden Blanco <bblanco@plumgrid.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Tested-by: default avatarBrenden Blanco <bblanco@plumgrid.com>
Reviewed-by: default avatarKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent 72e6f068
......@@ -128,12 +128,12 @@ static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
goto out;
}
static int skb_set_peeked(struct sk_buff *skb)
static struct sk_buff *skb_set_peeked(struct sk_buff *skb)
{
struct sk_buff *nskb;
if (skb->peeked)
return 0;
return skb;
/* We have to unshare an skb before modifying it. */
if (!skb_shared(skb))
......@@ -141,7 +141,7 @@ static int skb_set_peeked(struct sk_buff *skb)
nskb = skb_clone(skb, GFP_ATOMIC);
if (!nskb)
return -ENOMEM;
return ERR_PTR(-ENOMEM);
skb->prev->next = nskb;
skb->next->prev = nskb;
......@@ -154,7 +154,7 @@ static int skb_set_peeked(struct sk_buff *skb)
done:
skb->peeked = 1;
return 0;
return skb;
}
/**
......@@ -216,8 +216,9 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
*peeked = skb->peeked;
if (flags & MSG_PEEK) {
error = skb_set_peeked(skb);
if (error)
skb = skb_set_peeked(skb);
error = PTR_ERR(skb);
if (IS_ERR(skb))
goto unlock_err;
atomic_inc(&skb->users);
......
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