[linux-cifs-client] [PATCH] cifs: Fix broken mounts when SSH tunnel is used

[Jeff Layton]

On Tue, 18 Aug 2009 22:31:52 +0530
Suresh Jayaraman <sjayaraman at suse.de> wrote:

> It seems there is a regression that got introduced while Jeff fixed
> all the mount/umount races. While attempting to find whether a tcp
> session is already existing, we were not checking whether the "port"
> used are the same. When a second mount is attempted with a different
> "port=" option, it is being ignored. Because of this the cifs mounts
> that uses a SSH tunnel appears to be broken.
> 
> Steps to reproduce:
> 
> 1. create 2 shares
> # SSH Tunnel a SMB session
> 2. ssh -f -L 6111:127.0.0.1:445 root at localhost "sleep 86400"
> 3. ssh -f -L 6222:127.0.0.1:445 root at localhost "sleep 86400"
> 4. tcpdump -i lo 6111 &
> 5. mkdir -p /mnt/mnt1
> 6. mkdir -p /mnt/mnt2
> 7. mount.cifs //localhost/a /mnt/mnt1 -o username=guest,ip=127.0.0.1,port=6111
> #(shows tcpdump activity on port 6111)
> 8. mount.cifs //localhost/b /mnt/mnt2 -o username=guest,ip=127.0.0.1,port=6222
> #(shows tcpdump activity only on port 6111 and not on 6222
> 
> Fix this by adding a check to verify whether the port, before deciding that a
> existing tcp session is found and can be used. 
> 
> Signed-off-by: Suresh Jayaraman <sjayaraman at suse.de>
> ---
>  fs/cifs/connect.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 1f3345d..c00159c 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -1399,13 +1399,15 @@ cifs_find_tcp_session(struct sockaddr_storage *addr)
>  
>  		if (addr->ss_family == AF_INET &&
			^^^^
		The ss_family checks would look a lot cleaner as a
		switch statement. Can you fix that while you're at it?

>  		    (addr4->sin_addr.s_addr !=
> -		     server->addr.sockAddr.sin_addr.s_addr))
> +		     server->addr.sockAddr.sin_addr.s_addr ||
> +		     addr4->sin_port != server->addr.sockAddr.sin_port))
			^^^^
			I don't think addr4/addr6 have their ports set
			at this point. And in any case, you need to
			determine how to deal with the situation where
			someone hasn't set port= at all. In that case,
			this comparison will fail and you'll end up
			not sharing sockets when you could have.

>  			continue;
>  		else if (addr->ss_family == AF_INET6 &&
>  			 (!ipv6_addr_equal(&server->addr.sockAddr6.sin6_addr,
>  					   &addr6->sin6_addr) ||
>  			  server->addr.sockAddr6.sin6_scope_id !=
> -					   addr6->sin6_scope_id))
> +					   addr6->sin6_scope_id ||
> +			  server->addr.sockAddr6.sin6_port != addr6->sin6_port))
>  			continue;
>  
>  		++server->srv_count;


-- 
Jeff Layton <jlayton at redhat.com>