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authorHerbert Xu <herbert@gondor.apana.org.au>2015-08-04 15:42:47 +0800
committerDavid S. Miller <davem@davemloft.net>2015-08-06 21:55:47 -0700
commita0a2a6602496a45ae838a96db8b8173794b5d398 (patch)
tree5508d9f02066c30854b0c88b82fffc03c857adef /net/core
parent14d2b7c1a96ef37eb571599c73d4a1a606b964d6 (diff)
net: Fix skb_set_peeked use-after-free bug
The commit 738ac1ebb96d02e0d23bc320302a6ea94c612dec ("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: 738ac1ebb96d ("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>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/datagram.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 4967262b2707..617088aee21d 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -131,12 +131,12 @@ out_noerr:
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);

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