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From: Phil Sutter <phil@nwl•cc>
To: David Laight <David.Laight@ACULAB•COM>
Cc: Stephen Hemminger <stephen@networkplumber•org>,
	"netdev@vger•kernel.org" <netdev@vger•kernel.org>
Subject: Re: [iproute PATCH v2 1/7] ipntable: Make sure filter.name is NULL-terminated
Date: Fri, 18 Aug 2017 12:52:24 +0200	[thread overview]
Message-ID: <20170818105224.GG10864@orbyte.nwl.cc> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6DD005A7B4@AcuExch.aculab.com>

Hi David,

On Fri, Aug 18, 2017 at 09:19:16AM +0000, David Laight wrote:
> From: Phil Sutter
> > Sent: 17 August 2017 18:09
> > To: Stephen Hemminger
> > Cc: netdev@vger•kernel.org
> > Subject: [iproute PATCH v2 1/7] ipntable: Make sure filter.name is NULL-terminated
> > 
> > Signed-off-by: Phil Sutter <phil@nwl•cc>
> > ---
> >  ip/ipntable.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/ip/ipntable.c b/ip/ipntable.c
> > index 879626ee4f491..7be1f04d33d90 100644
> > --- a/ip/ipntable.c
> > +++ b/ip/ipntable.c
> > @@ -633,7 +633,8 @@ static int ipntable_show(int argc, char **argv)
> >  		} else if (strcmp(*argv, "name") == 0) {
> >  			NEXT_ARG();
> > 
> > -			strncpy(filter.name, *argv, sizeof(filter.name));
> > +			strncpy(filter.name, *argv, sizeof(filter.name) - 1);
> > +			filter.name[sizeof(filter.name) - 1] = '\0';
> 
> Why not check for overflow instead?
> 			if (filter.name[sizeof(filter.name) - 1])
> 				usage("filer name too long");

sizeof(filter.name) is 1024, which is maybe a bit over the top for
something a user would input. So I found a better way avoiding all this
at once: I made filter.name a const char *, then just assigned *argv to
it. This should be safe since rtnl_dump_filter() and therefore
print_ntable() callback is called from inside ipntable_show() so *argv
is not accessed outside of it's scope.

What do you think?

Thanks, Phil

next prev parent reply	other threads:[~2017-08-18 10:52 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-17 17:09 [iproute PATCH v2 0/7] Covscan: Fixes for string termination Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 1/7] ipntable: Make sure filter.name is NULL-terminated Phil Sutter
2017-08-18  9:19   ` David Laight
2017-08-18 10:52     ` Phil Sutter [this message]
2017-08-18 16:32       ` David Laight
2017-08-18 16:52         ` Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 2/7] xfrm_state: Make sure alg_name " Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 3/7] lib/fs: Fix format string in find_fs_mount() Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 4/7] lib/inet_proto: Make sure destination buffers are NULL-terminated Phil Sutter
2017-08-18 16:37   ` Stephen Hemminger
2017-08-18 16:55     ` Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 5/7] lnstat_util: Simplify alloc_and_open() a bit Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 6/7] tc/m_xt: Fix for potential string buffer overflows Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 7/7] lib/ll_map: Make sure im->name is NULL-terminated Phil Sutter
2017-08-18 16:33   ` Stephen Hemminger

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