Commit a0a2a660 authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller

net: Fix skb_set_peeked use-after-free bug

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>
parent 14d2b7c1
...@@ -131,12 +131,12 @@ static int wait_for_more_packets(struct sock *sk, int *err, long *timeo_p, ...@@ -131,12 +131,12 @@ static int wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
goto out; 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; struct sk_buff *nskb;
if (skb->peeked) if (skb->peeked)
return 0; return skb;
/* We have to unshare an skb before modifying it. */ /* We have to unshare an skb before modifying it. */
if (!skb_shared(skb)) if (!skb_shared(skb))
...@@ -144,7 +144,7 @@ static int skb_set_peeked(struct sk_buff *skb) ...@@ -144,7 +144,7 @@ static int skb_set_peeked(struct sk_buff *skb)
nskb = skb_clone(skb, GFP_ATOMIC); nskb = skb_clone(skb, GFP_ATOMIC);
if (!nskb) if (!nskb)
return -ENOMEM; return ERR_PTR(-ENOMEM);
skb->prev->next = nskb; skb->prev->next = nskb;
skb->next->prev = nskb; skb->next->prev = nskb;
...@@ -157,7 +157,7 @@ static int skb_set_peeked(struct sk_buff *skb) ...@@ -157,7 +157,7 @@ static int skb_set_peeked(struct sk_buff *skb)
done: done:
skb->peeked = 1; skb->peeked = 1;
return 0; return skb;
} }
/** /**
...@@ -229,8 +229,9 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, ...@@ -229,8 +229,9 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
continue; continue;
} }
error = skb_set_peeked(skb); skb = skb_set_peeked(skb);
if (error) error = PTR_ERR(skb);
if (IS_ERR(skb))
goto unlock_err; goto unlock_err;
atomic_inc(&skb->users); atomic_inc(&skb->users);
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment