Re: [PATCH nft 3/3] parser_bison: fix length check for ifname in ifname_expr_alloc()

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, Oct 23, 2023 at 07:15:10PM +0200, Pablo Neira Ayuso wrote:
> On Mon, Oct 23, 2023 at 07:00:47PM +0200, Thomas Haller wrote:
> > IFNAMSIZ is 16, and the allowed byte length of the name is one less than
> > that. Fix the length check and adjust a test for covering the longest
> > allowed interface name.
> > 
> > This is obviously a change in behavior, because previously interface
> > names with length 16 were accepted and were silently truncated along the
> > way. Now they are rejected as invalid.
> > 
> > Fixes: fa52bc225806 ('parser: reject zero-length interface names')
> > Signed-off-by: Thomas Haller <thaller@redhat.com>
> > ---
> >  src/parser_bison.y                                | 3 ++-
> >  tests/shell/testcases/chains/0042chain_variable_0 | 7 +------
> >  2 files changed, 3 insertions(+), 7 deletions(-)
> > 
> > diff --git a/src/parser_bison.y b/src/parser_bison.y
> > index f0652ba651c6..9bfc3cdb2d12 100644
> > --- a/src/parser_bison.y
> > +++ b/src/parser_bison.y
> > @@ -16,6 +16,7 @@
> >  #include <stdio.h>
> >  #include <inttypes.h>
> >  #include <syslog.h>
> > +#include <net/if.h>
> >  #include <netinet/ip.h>
> >  #include <netinet/tcp.h>
> >  #include <netinet/if_ether.h>
> > @@ -158,7 +159,7 @@ static struct expr *ifname_expr_alloc(const struct location *location,
> >  		return NULL;
> >  	}
> >  
> > -	if (length > 16) {
> > +	if (length >= IFNAMSIZ) {
> >  		xfree(name);
> >  		erec_queue(error(location, "interface name too long"), queue);
> >  		return NULL;
> > diff --git a/tests/shell/testcases/chains/0042chain_variable_0 b/tests/shell/testcases/chains/0042chain_variable_0
> > index 739dc05a1777..a4b929f7344c 100755
> > --- a/tests/shell/testcases/chains/0042chain_variable_0
> > +++ b/tests/shell/testcases/chains/0042chain_variable_0
> > @@ -26,18 +26,13 @@ table netdev filter2 {
> >  
> >  rc=0
> >  $NFT -f - <<< $EXPECTED || rc=$?
> > -test "$rc" = 0
> > +test "$rc" = 1
> >  cat <<EOF | $DIFF -u <($NFT list ruleset) -
> >  table netdev filter1 {
> >  	chain Main_Ingress1 {
> >  		type filter hook ingress device "lo" priority -500; policy accept;
> >  	}
> >  }
> > -table netdev filter2 {
> > -	chain Main_Ingress2 {
> > -		type filter hook ingress devices = { d23456789012345, lo } priority -500; policy accept;
> > -	}
> > -}
> 
> Please, do not remove it, fix this test.

Or maybe I am missing the reason for this change? It seems this
d23456789012345 was added to your previous patch in this series.

Thanks!