netdev - Re: [PATCH iproute2] ip route: check ftell, fseek return value

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Date:   Wed, 7 Sep 2016 21:50:40 +0800
From:   Hangbin Liu <haliu@...hat.com>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     "'Hangbin Liu'" <liuhangbin@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Phil Sutter <phil@....cc>,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [PATCH iproute2] ip route: check ftell, fseek return value

On Tue, Sep 06, 2016 at 11:18:00AM +0000, David Laight wrote:
> From: Hangbin Liu
> > Sent: 06 September 2016 07:40
> > ftell() may return -1 in error case, which is not handled and therefore pass a
> > negative offset to fseek(). The return code of fseek() is also not checked.
> > 
> > Reported-by: Phil Sutter <phil@....cc>
> > Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> > ---
> >  ip/iproute.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/ip/iproute.c b/ip/iproute.c
> > index 3da23af..ba877dc 100644
> > --- a/ip/iproute.c
> > +++ b/ip/iproute.c
> > @@ -1859,7 +1859,11 @@ static int iproute_restore(void)
> >  	if (route_dump_check_magic())
> >  		exit(-1);
> > 
> > -	pos = ftell(stdin);
> > +	if ((pos = ftell(stdin)) == -1) {
> 
> Don't put assignments in conditionals.
> 
> > +		perror("Failed to restore: ftell");
> > +		exit(errno);
> 
> errno is not a valid argument to exit().

Hi David,

Thanks for the advice. I will send PATCHv2 to fix them.

> 
> ...
> 
> Actually WTF is this code trying to do.
> stdin is vere likely to be a pipe, so expecting to seek on it
> seems very likely to fail.

I will fix the return code handle issue first and try investigate the pipe
issue later.

Regards
Hangbin