Messages in this thread Patch in this message | | | Date | Tue, 30 Jun 2009 17:23:10 -0700 | From | Greg KH <> | Subject | [patch 021/108] tun: Fix unregister race |
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2.6.30-stable review patch. If anyone has any objections, please let us know.
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From: Eric W. Biederman <ebiederm@aristanetworks.com>
[ Upstream commit f0a4d0e5b5bfd271e6737f7c095994835b70d450 ]
It is possible for tun_chr_close to race with dellink on the a tun device. In which case if __tun_get runs before dellink but dellink runs before tun_chr_close calls unregister_netdevice we will attempt to unregister the netdevice after it is already gone.
The two cases are already serialized on the rtnl_lock, so I have gone for the cheap simple fix of moving rtnl_lock to cover __tun_get in tun_chr_close. Eliminating the possibility of the tun device being unregistered between __tun_get and unregister_netdevice in tun_chr_close.
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com> Tested-by: David Woodhouse <David.Woodhouse@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/net/tun.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
--- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1275,21 +1275,22 @@ static int tun_chr_open(struct inode *in static int tun_chr_close(struct inode *inode, struct file *file) { struct tun_file *tfile = file->private_data; - struct tun_struct *tun = __tun_get(tfile); + struct tun_struct *tun; + rtnl_lock(); + tun = __tun_get(tfile); if (tun) { DBG(KERN_INFO "%s: tun_chr_close\n", tun->dev->name); - rtnl_lock(); __tun_detach(tun); /* If desireable, unregister the netdevice. */ if (!(tun->flags & TUN_PERSIST)) unregister_netdevice(tun->dev); - rtnl_unlock(); } + rtnl_unlock(); tun = tfile->tun; if (tun)
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