Patchwork caif: fix two caif_connect() bugs

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Submitter Eric Dumazet
Date Oct. 5, 2010, 8:42 a.m.
Message ID <1286268128.2796.27.camel@edumazet-laptop>
Download mbox | patch
Permalink /patch/66771/
State Accepted
Delegated to: David Miller
Headers show

Comments

Eric Dumazet - Oct. 5, 2010, 8:42 a.m.
caif_connect() might dereference a netdevice after dev_put() it.

It also doesnt check dev_get_by_index() return value and could
dereference a NULL pointer.

Fix it, using RCU to avoid taking a reference.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Sjur Braendeland <sjur.brandeland@stericsson.com>
---
 net/caif/caif_socket.c |   21 +++++++++++++++------
 1 files changed, 15 insertions(+), 6 deletions(-)



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David Miller - Oct. 6, 2010, 3:38 a.m.
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 05 Oct 2010 10:42:08 +0200

> caif_connect() might dereference a netdevice after dev_put() it.
> 
> It also doesnt check dev_get_by_index() return value and could
> dereference a NULL pointer.
> 
> Fix it, using RCU to avoid taking a reference.
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

Applied, thanks Eric.
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Patch

diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 8ce9047..4bf28f2 100644
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -827,6 +827,7 @@  static int caif_connect(struct socket *sock, struct sockaddr *uaddr,
 	long timeo;
 	int err;
 	int ifindex, headroom, tailroom;
+	unsigned int mtu;
 	struct net_device *dev;
 
 	lock_sock(sk);
@@ -896,15 +897,23 @@  static int caif_connect(struct socket *sock, struct sockaddr *uaddr,
 		cf_sk->sk.sk_state = CAIF_DISCONNECTED;
 		goto out;
 	}
-	dev = dev_get_by_index(sock_net(sk), ifindex);
+
+	err = -ENODEV;
+	rcu_read_lock();
+	dev = dev_get_by_index_rcu(sock_net(sk), ifindex);
+	if (!dev) {
+		rcu_read_unlock();
+		goto out;
+	}
 	cf_sk->headroom = LL_RESERVED_SPACE_EXTRA(dev, headroom);
+	mtu = dev->mtu;
+	rcu_read_unlock();
+
 	cf_sk->tailroom = tailroom;
-	cf_sk->maxframe = dev->mtu - (headroom + tailroom);
-	dev_put(dev);
+	cf_sk->maxframe = mtu - (headroom + tailroom);
 	if (cf_sk->maxframe < 1) {
-		pr_warning("CAIF: %s(): CAIF Interface MTU too small (%d)\n",
-			__func__, dev->mtu);
-		err = -ENODEV;
+		pr_warning("CAIF: %s(): CAIF Interface MTU too small (%u)\n",
+			   __func__, mtu);
 		goto out;
 	}