From: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Date: Sun, 5 Jul 2009 19:48:35 +0000 (+0000)
Subject: tun/tap: Fix crashes if open() /dev/net/tun and then poll() it.
X-Git-Tag: v2.6.31-rc3~40^2~15
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=3c8a9c63d5fd738c261bd0ceece04d9c8357ca13;p=platform%2Fupstream%2Fkernel-adaptation-pc.git

tun/tap: Fix crashes if open() /dev/net/tun and then poll() it.

Fix NULL pointer dereference in tun_chr_pool() introduced by commit
33dccbb050bbe35b88ca8cf1228dcf3e4d4b3554 ("tun: Limit amount of queued
packets per device") and triggered by this code:

	int fd;
	struct pollfd pfd;
	fd = open("/dev/net/tun", O_RDWR);
	pfd.fd = fd;
	pfd.events = POLLIN | POLLOUT;
	poll(&pfd, 1, 0);

Reported-by: Eugene Kapun <abacabadabacaba@gmail.com>
Signed-off-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index b393536..027f7ab 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -486,12 +486,14 @@ static unsigned int tun_chr_poll(struct file *file, poll_table * wait)
 {
 	struct tun_file *tfile = file->private_data;
 	struct tun_struct *tun = __tun_get(tfile);
-	struct sock *sk = tun->sk;
+	struct sock *sk;
 	unsigned int mask = 0;
 
 	if (!tun)
 		return POLLERR;
 
+	sk = tun->sk;
+
 	DBG(KERN_INFO "%s: tun_chr_poll\n", tun->dev->name);
 
 	poll_wait(file, &tun->socket.wait, wait);