linux-kernel - [PATCH 3.19.y-ckt 085/102] net: Fix skb_set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1442944358-1248-86-git-send-email-kamal@canonical.com>
Date:	Tue, 22 Sep 2015 10:52:21 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 085/102] net: Fix skb_set_peeked use-after-free bug

3.19.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Herbert Xu <herbert@...dor.apana.org.au>

commit a0a2a6602496a45ae838a96db8b8173794b5d398 upstream.

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@...mgrid.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Tested-by: Brenden Blanco <bblanco@...mgrid.com>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 net/core/datagram.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 91dbcfa..f5cce20 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);
-- 
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/