linux-kernel - Re: [PATCH] SUNRPC: Add a check for gss_release

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Message-ID: <20210407153458.GA28924@fieldses.org>
Date:   Wed, 7 Apr 2021 11:34:58 -0400
From:   "J. Bruce Fields" <bfields@...ldses.org>
To:     Aditya Pakki <pakki001@....edu>
Cc:     Chuck Lever <chuck.lever@...cle.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Dave Wysochanski <dwysocha@...hat.com>,
        linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] SUNRPC: Add a check for gss_release_msg

On Tue, Apr 06, 2021 at 07:16:56PM -0500, Aditya Pakki wrote:
> In gss_pipe_destroy_msg(), in case of error in msg, gss_release_msg
> deletes gss_msg. The patch adds a check to avoid a potential double
> free.

We're already dereferenced msg.  Nothing has set gss_msg to NULL.  It's
the gss_msg->count reference count that's supposed to prevent double
frees.

Did you see an actual bug or warning from some tool, and if so, could
you share the details?

--b.

> 
> Signed-off-by: Aditya Pakki <pakki001@....edu>
> ---
>  net/sunrpc/auth_gss/auth_gss.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
> index 5f42aa5fc612..eb52eebb3923 100644
> --- a/net/sunrpc/auth_gss/auth_gss.c
> +++ b/net/sunrpc/auth_gss/auth_gss.c
> @@ -848,7 +848,8 @@ gss_pipe_destroy_msg(struct rpc_pipe_msg *msg)
>  			warn_gssd();
>  		gss_release_msg(gss_msg);
>  	}
> -	gss_release_msg(gss_msg);
> +	if (gss_msg)
> +		gss_release_msg(gss_msg);
>  }
>  
>  static void gss_pipe_dentry_destroy(struct dentry *dir,
> -- 
> 2.25.1