Patchwork tun: don't zeroize sock->file on detach

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Submitter Stanislav Kinsbursky
Date Aug. 9, 2012, 12:50 p.m.
Message ID <20120809124436.5156.26944.stgit@localhost.localdomain>
Download mbox | patch
Permalink /patch/176076/
State Accepted
Delegated to: David Miller
Headers show

Comments

Stanislav Kinsbursky - Aug. 9, 2012, 12:50 p.m.
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.

Cc: stable@vger.kernel.org
Reported-by: Ruan Zhijie <ruanzhijie@hotmail.com>
Tested-by: Ruan Zhijie <ruanzhijie@hotmail.com>
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
 drivers/net/tun.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)


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David Miller - Aug. 9, 2012, 11:16 p.m.
From: Stanislav Kinsbursky <skinsbursky@parallels.com>
Date: Thu, 09 Aug 2012 16:50:40 +0400

> 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.
> 
> Cc: stable@vger.kernel.org
> Reported-by: Ruan Zhijie <ruanzhijie@hotmail.com>
> Tested-by: Ruan Zhijie <ruanzhijie@hotmail.com>
> Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
> Acked-by: Eric Dumazet <edumazet@google.com>
> Acked-by: Yuchung Cheng <ycheng@google.com>
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>

Applied, thanks.
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Stanislav Kinsbursky - Aug. 21, 2012, 4:04 p.m.
10.08.2012 03:16, David Miller пишет:
> From: Stanislav Kinsbursky <skinsbursky@parallels.com>
> Date: Thu, 09 Aug 2012 16:50:40 +0400
>
>> 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.
>>
>> Cc: stable@vger.kernel.org
>> Reported-by: Ruan Zhijie <ruanzhijie@hotmail.com>
>> Tested-by: Ruan Zhijie <ruanzhijie@hotmail.com>
>> Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
>> Acked-by: Eric Dumazet <edumazet@google.com>
>> Acked-by: Yuchung Cheng <ycheng@google.com>
>> Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
>
> Applied, thanks.
>

Hi, David.
I found out, that this commit: b09e786bd1dd66418b69348cb110f3a64764626a
was previous attempt to fix the problem.
I believe this commit have to be dropped.
Neal Cardwell - Aug. 21, 2012, 5:18 p.m.
On Tue, Aug 21, 2012 at 12:04 PM, Stanislav Kinsbursky
<skinsbursky@parallels.com> wrote:
> 10.08.2012 03:16, David Miller пишет:
>
>> From: Stanislav Kinsbursky <skinsbursky@parallels.com>
>> Date: Thu, 09 Aug 2012 16:50:40 +0400
>>
>>> 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.
>>>
>>> Cc: stable@vger.kernel.org
>>> Reported-by: Ruan Zhijie <ruanzhijie@hotmail.com>
>>> Tested-by: Ruan Zhijie <ruanzhijie@hotmail.com>
>>> Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
>>> Acked-by: Eric Dumazet <edumazet@google.com>
>>> Acked-by: Yuchung Cheng <ycheng@google.com>
>>> Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
>>
>>
>> Applied, thanks.
>>
>
> Hi, David.
> I found out, that this commit: b09e786bd1dd66418b69348cb110f3a64764626a
> was previous attempt to fix the problem.
> I believe this commit have to be dropped.

Have you tried testing with that commit reverted? AFAICT from reading
the code, if you revert b09e786bd1dd66418b69348cb110f3a64764626a then
the sockets_in_use count becomes incorrect, because sock_release()
will be calling this_cpu_sub() for each tun socket teardown when there
was no corresponding this_cpu_add() for the tun socket (because the
tun socket is not allocated with sock_alloc()).

Can you sketch in more detail why that commit should be dropped?

neal
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Patch

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);
 
 	/* Drop read queue */