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

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Date:   Sat, 7 Nov 2020 13:49:40 +0000
From:   Alex Dewar <alex.dewar90@...il.com>
To:     "J. Bruce Fields" <bfields@...ldses.org>
Cc:     Alex Dewar <alex.dewar90@...il.com>,
        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()

On Fri, Nov 06, 2020 at 05:07:21PM -0500, J. Bruce Fields wrote:
> 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.

That looks like a cleaner fix. Thanks for looking anyhow and sorry for
the noise!

> 
> 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