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SubjectRe: PROBLEM: tun/tap crashes if open() /dev/net/tun and then poll() it.
On Mon, 6 Jul 2009 09:12:30 +0800
Herbert Xu <herbert@gondor.apana.org.au> wrote:

> On Mon, Jul 06, 2009 at 12:11:14AM +0200, Mariusz Kozlowski wrote:
> >
> > Can you try this patch?
...
> Good catch. Can you please resend with a sign-off?

Sure. Just wanted to wait for confirmation from Eugene.

Fix NULL pointer dereference in tun_chr_pool() introduced by
commit 33dccbb050bbe35b88ca8cf1228dcf3e4d4b3554 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>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a1b0697..bcbb25e 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -482,12 +482,14 @@ 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, &tfile->read_wait, wait);


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