Re: [PATCH] cifs: fix potential double put of TCP session reference

[Suresh Jayaraman <sjayaraman-l3A5Bk7waGM@public.gmane.org>]

On 09/13/2010 11:32 PM, Jeff Layton wrote:
> cifs_get_smb_ses must be called on a server pointer on which it holds an
> active reference. It first does a search for an existing SMB session. If
> it finds one, it'll put the server reference and then try to ensure that
> the negprot is done, etc.
> 
> If it encounters an error at that point then it'll return an error.
> There's a potential problem here though. When cifs_get_smb_ses returns
> an error, the caller will also put the TCP server reference leading to a
> double-put.
> 
> Fix this by having cifs_get_smb_ses only put the server reference if
> it found an existing session that it could use and isn't returning an
> error.
> 
> Signed-off-by: Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  fs/cifs/connect.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 67dad54..88c84a3 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -1706,9 +1706,6 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
>  	if (ses) {
>  		cFYI(1, "Existing smb sess found (status=%d)", ses->status);
>  
> -		/* existing SMB ses has a server reference already */
> -		cifs_put_tcp_session(server);
> -
>  		mutex_lock(&ses->session_mutex);
>  		rc = cifs_negotiate_protocol(xid, ses);
>  		if (rc) {
> @@ -1731,6 +1728,9 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
>  			}
>  		}
>  		mutex_unlock(&ses->session_mutex);
> +
> +		/* existing SMB ses has a server reference already */
> +		cifs_put_tcp_session(server);
>  		FreeXid(xid);
>  		return ses;
>  	}

Looks correct to me.

Reviewed-by: Suresh Jayaraman <sjayaraman-l3A5Bk7waGM@public.gmane.org>