Re: [iproute PATCH v2 4/5] tc/tc_filter: Make sure filter name is not empty

[Phil Sutter]

On Fri, Aug 18, 2017 at 04:34:44PM +, David Laight wrote:
> From: Phil Sutter
> > Sent: 18 August 2017 12:16
> > On Fri, Aug 18, 2017 at 09:30:35AM +, David Laight wrote:
> > > From: Phil Sutter
> > > > Sent: 17 August 2017 18:10
> > > > The later check for 'k[0] != 0' requires a non-empty filter name,
> > > > otherwise NULL pointer dereference in 'q' might happen.
> > > >
> > > > Signed-off-by: Phil Sutter 
> > > > ---
> > > >  tc/tc_filter.c | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/tc/tc_filter.c b/tc/tc_filter.c
> > > > index b13fb9185d4fd..a799edb35886d 100644
> > > > --- a/tc/tc_filter.c
> > > > +++ b/tc/tc_filter.c
> > > > @@ -412,6 +412,9 @@ static int tc_filter_get(int cmd, unsigned int 
> > > > flags, int argc, char **argv)
> > > > usage();
> > > > return 0;
> > > > } else {
> > > > +   if (!strlen(*argv))
> > > > +   invarg("invalid filter name", *argv);
> > >
> > > That is nearly as bad as:
> > >   p[strlen(p)] = 0;
> > 
> > Hey, it's not impossible! I could call tc like so:
> > 
> > | # tc filter get protocol ip prio 1 ""
> 
> You missed the point. Just check **argv there is no need to
> determine the length just to check it is non-zero.

Oh, hehe. Thanks for the short-cut!

Thanks, PHil

RE: [iproute PATCH v2 4/5] tc/tc_filter: Make sure filter name is not empty

[David Laight]

From: Phil Sutter
> Sent: 18 August 2017 12:16
> On Fri, Aug 18, 2017 at 09:30:35AM +, David Laight wrote:
> > From: Phil Sutter
> > > Sent: 17 August 2017 18:10
> > > The later check for 'k[0] != 0' requires a non-empty filter name,
> > > otherwise NULL pointer dereference in 'q' might happen.
> > >
> > > Signed-off-by: Phil Sutter 
> > > ---
> > >  tc/tc_filter.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/tc/tc_filter.c b/tc/tc_filter.c
> > > index b13fb9185d4fd..a799edb35886d 100644
> > > --- a/tc/tc_filter.c
> > > +++ b/tc/tc_filter.c
> > > @@ -412,6 +412,9 @@ static int tc_filter_get(int cmd, unsigned int flags, 
> > > int argc, char **argv)
> > >   usage();
> > >   return 0;
> > >   } else {
> > > + if (!strlen(*argv))
> > > + invarg("invalid filter name", *argv);
> >
> > That is nearly as bad as:
> > p[strlen(p)] = 0;
> 
> Hey, it's not impossible! I could call tc like so:
> 
> | # tc filter get protocol ip prio 1 ""

You missed the point. Just check **argv there is no need to
determine the length just to check it is non-zero.

David

Re: [iproute PATCH v2 4/5] tc/tc_filter: Make sure filter name is not empty

[Phil Sutter]

On Fri, Aug 18, 2017 at 09:30:35AM +, David Laight wrote:
> From: Phil Sutter
> > Sent: 17 August 2017 18:10
> > The later check for 'k[0] != 0' requires a non-empty filter name,
> > otherwise NULL pointer dereference in 'q' might happen.
> > 
> > Signed-off-by: Phil Sutter 
> > ---
> >  tc/tc_filter.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/tc/tc_filter.c b/tc/tc_filter.c
> > index b13fb9185d4fd..a799edb35886d 100644
> > --- a/tc/tc_filter.c
> > +++ b/tc/tc_filter.c
> > @@ -412,6 +412,9 @@ static int tc_filter_get(int cmd, unsigned int flags, 
> > int argc, char **argv)
> > usage();
> > return 0;
> > } else {
> > +   if (!strlen(*argv))
> > +   invarg("invalid filter name", *argv);
> 
> That is nearly as bad as:
>   p[strlen(p)] = 0;

Hey, it's not impossible! I could call tc like so:

| # tc filter get protocol ip prio 1 ""

What's funny about it is that the first call to matches() in
tc_filter_get() will catch the empty last parameter:

| # tc filter get prio 1 protocol ip ""
| Command line is not complete. Try option "help"
| # ./tc/tc filter get prio 1 protocol ip "" ""
| Error: duplicate "priority": "" is the second value.

Cheers, Phil

RE: [iproute PATCH v2 4/5] tc/tc_filter: Make sure filter name is not empty

[David Laight]

From: Phil Sutter
> Sent: 17 August 2017 18:10
> The later check for 'k[0] != 0' requires a non-empty filter name,
> otherwise NULL pointer dereference in 'q' might happen.
> 
> Signed-off-by: Phil Sutter 
> ---
>  tc/tc_filter.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/tc/tc_filter.c b/tc/tc_filter.c
> index b13fb9185d4fd..a799edb35886d 100644
> --- a/tc/tc_filter.c
> +++ b/tc/tc_filter.c
> @@ -412,6 +412,9 @@ static int tc_filter_get(int cmd, unsigned int flags, int 
> argc, char **argv)
>   usage();
>   return 0;
>   } else {
> + if (!strlen(*argv))
> + invarg("invalid filter name", *argv);

That is nearly as bad as:
p[strlen(p)] = 0;

> +
>   strncpy(k, *argv, sizeof(k)-1);
> 
>   q = get_filter_kind(k);
> --
> 2.13.1