linux-kernel - Re: [PATCH] net/sunrpc: Fix return value from proc_do

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Message-ID: <20201106220721.GE26028@fieldses.org>
Date:   Fri, 6 Nov 2020 17:07:21 -0500
From:   "J. Bruce Fields" <bfields@...ldses.org>
To:     Alex Dewar <alex.dewar90@...il.com>
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>,
        Artur Molchanov <arturmolchanov@...il.com>,
        linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/sunrpc: Fix return value from proc_do_xprt()

Whoops, got 3 independent patches for this and overlooked this one.  See
https://lore.kernel.org/linux-nfs/20201106205959.GB26028@fieldses.org/T/#t

--b.

On Sat, Oct 24, 2020 at 03:52:40PM +0100, Alex Dewar wrote:
> Commit c09f56b8f68d ("net/sunrpc: Fix return value for sysctl
> sunrpc.transports") attempted to add error checking for the call to
> memory_read_from_buffer(), however its return value was assigned to a
> size_t variable, so any negative values would be lost in the cast. Fix
> this.
> 
> Addresses-Coverity-ID: 1498033: Control flow issues (NO_EFFECT)
> Fixes: c09f56b8f68d ("net/sunrpc: Fix return value for sysctl sunrpc.transports")
> Signed-off-by: Alex Dewar <alex.dewar90@...il.com>
> ---
>  net/sunrpc/sysctl.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sunrpc/sysctl.c b/net/sunrpc/sysctl.c
> index a18b36b5422d..c95a2b84dd95 100644
> --- a/net/sunrpc/sysctl.c
> +++ b/net/sunrpc/sysctl.c
> @@ -62,6 +62,7 @@ rpc_unregister_sysctl(void)
>  static int proc_do_xprt(struct ctl_table *table, int write,
>  			void *buffer, size_t *lenp, loff_t *ppos)
>  {
> +	ssize_t bytes_read;
>  	char tmpbuf[256];
>  	size_t len;
>  
> @@ -70,12 +71,14 @@ static int proc_do_xprt(struct ctl_table *table, int write,
>  		return 0;
>  	}
>  	len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));
> -	*lenp = memory_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len);
> +	bytes_read = memory_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len);
>  
> -	if (*lenp < 0) {
> +	if (bytes_read < 0) {
>  		*lenp = 0;
>  		return -EINVAL;
>  	}
> +
> +	*lenp = bytes_read;
>  	return 0;
>  }
>  
> -- 
> 2.29.1