Re: [RFC PATCH] tun: don't zeroize sock->file on detach

On Wed, Aug 8, 2012 at 5:53 AM, Stanislav Kinsbursky
[off-list ref] wrote:

Hi, Dave.
What about this patch?


On Wed, Jul 11, 2012 at 03:48:20PM +0400, Stanislav Kinsbursky wrote:

quoted

This is a fix for bug, introduced in 3.4 kernel by commit
1ab5ecb90cb6a3df1476e052f76a6e8f6511cb3d, which, among other things,
replaced
simple sock_put() by sk_release_kernel(). Below is sequence, which leads
to
oops for non-persistent devices:

tun_chr_close()
tun_detach()                            <== tun->socket.file = NULL
tun_free_netdev()
sk_release_sock()
sock_release(sock->file == NULL)
iput(SOCK_INODE(sock))                  <== dereference on NULL pointer

This patch just removes zeroing of socket's file from __tun_detach().
sock_release() will do this.

Signed-off-by: Stanislav Kinsbursky <redacted>

Acked-by: Yuchung Cheng <redacted>

I has tested this patch and it works (so my kernel stops crashing
using tun devices).

quoted

---
 drivers/net/tun.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 987aeef..c1639f3 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c

@@ -185,7 +185,6 @@ static void __tun_detach(struct tun_struct *tun)
        netif_tx_lock_bh(tun->dev);
        netif_carrier_off(tun->dev);
        tun->tfile = NULL;
-       tun->socket.file = NULL;
        netif_tx_unlock_bh(tun->dev);

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