Re: [dpdk-dev] [PATCH 3/3] app/pdump: fix string overflow

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Jun 22, 2016 at 12:16:27PM +0530, Anupam Kapoor wrote:
> >       if (!strcmp(key, PDUMP_RX_DEV_ARG)) {
> > -             strncpy(pt->rx_dev, value, strlen(value));
> > +             strncpy(pt->rx_dev, value, sizeof(pt->rx_dev)-1);
> 
> I guess size-1 is to give room for terminating null byte, but for this
> case is it guarantied that pt->rx_dev last byte is NULL?
> 
> why not just use a snprintf(...) here since it has better error behavior ?
> although compared to str*cpy it might be a bit slow, but hopefully that
> should be ok ?
> 

Definite +1. For safely copying strings I think snprintf is often the easiest
API to use.

/Bruce

> --
> thanks
> anupam
> 
> 
> On Tue, Jun 21, 2016 at 10:51 PM, Ferruh Yigit <ferruh.yigit@intel.com>
> wrote:
> 
> > On 6/21/2016 4:18 PM, Reshma Pattan wrote:
> > > using source length in strncpy can cause destination
> > > overflow if destination length is not big enough to
> > > handle the source string. Changes are made to use destination
> > > size instead of source length in strncpy.
> > >
> > > Coverity issue 127351: string overflow
> > >
> > > Fixes: caa7028276b8 ("app/pdump: add tool for packet capturing")
> > >
> > > Signed-off-by: Reshma Pattan <reshma.pattan@intel.com>
> > > ---
> > >  app/pdump/main.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/app/pdump/main.c b/app/pdump/main.c
> > > index f8923b9..af92ef3 100644
> > > --- a/app/pdump/main.c
> > > +++ b/app/pdump/main.c
> > > @@ -217,12 +217,12 @@ parse_rxtxdev(const char *key, const char *value,
> > void *extra_args)
> > >       struct pdump_tuples *pt = extra_args;
> > >
> > >       if (!strcmp(key, PDUMP_RX_DEV_ARG)) {
> > > -             strncpy(pt->rx_dev, value, strlen(value));
> > > +             strncpy(pt->rx_dev, value, sizeof(pt->rx_dev)-1);
> >
> > I guess size-1 is to give room for terminating null byte, but for this
> > case is it guarantied that pt->rx_dev last byte is NULL?
> >
> >
> 
> 
> -- 
> In the beginning was the lambda, and the lambda was with Emacs, and Emacs
> was the lambda.