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net: Fix skb_set_peeked use-after-free bug

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The commit 738ac1ebb9 ("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: 738ac1ebb9 ("net: Clone skb before setting peeked flag")
Reported-by: Brenden Blanco <bblanco@plumgrid.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Brenden Blanco <bblanco@plumgrid.com>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2015-08-04 15:42:47 +08:00 committed by David S. Miller
parent 14d2b7c1a9
commit a0a2a66024
1 changed files with 7 additions and 6 deletions
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13
net/core/datagram.c
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@ -131,12 +131,12 @@ static int wait_for_more_packets(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))
@ -144,7 +144,7 @@ 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;
@ -157,7 +157,7 @@ static int skb_set_peeked(struct sk_buff *skb)
done:
skb->peeked = 1;
return 0;
return skb;
}
/**
@ -229,8 +229,9 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
continue;
}
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);