On Fri, Mar 04, 2022 at 01:15:59PM +0100, Phil Sutter wrote:
> On Fri, Mar 04, 2022 at 12:11:53PM +0100, Pablo Neira Ayuso wrote:
> > Hi Phil,
> >
> > On Fri, Mar 04, 2022 at 11:37:11AM +0100, Phil Sutter wrote:
> > > When trying to add a rule which contains an anonymous chain to a
> > > non-existent chain, string_misspell_update() is called with a NULL
> > > string because the anonymous chain has no name. Avoid this by making the
> > > function NULL-pointer tolerant.
> > >
> > > c330152b7f777 ("src: support for implicit chain bindings")
> > >
> > > Signed-off-by: Phil Sutter <phil@xxxxxx>
> > > ---
> > > src/misspell.c | 4 ++--
> > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/src/misspell.c b/src/misspell.c
> > > index 6536d7557a445..f213a240005e6 100644
> > > --- a/src/misspell.c
> > > +++ b/src/misspell.c
> > > @@ -80,8 +80,8 @@ int string_misspell_update(const char *a, const char *b,
> > > {
> > > unsigned int len_a, len_b, max_len, min_len, distance, threshold;
> > >
> > > - len_a = strlen(a);
> > > - len_b = strlen(b);
> > > + len_a = a ? strlen(a) : 0;
> > > + len_b = b ? strlen(b) : 0;
> >
> > string_distance() assumes non-NULL too.
>
> Which is called from string_misspell_update() only which with my patch
> returns early due to 'max_len <= 1'.
>
> > probably shortcircuit chain_lookup_fuzzy() earlier since h->chain.name
> > is always NULL, to avoid the useless loop.
>
> Fine with me, too! What about allocating a name for the anonymous chain
> instead?
A dummy name could be allocated, but the kernel does not need the
chain name at this stage (it uses the ephemeral 32-bit chain ID
instead which is only valid in the netlink batch).
Probably set_lookup_fuzzy() should also short-circuit early the
misspell logic for anonymous sets.
> I guess similar treatment as with sets would make sense. Might
> also help with netlink debug output:
>
> | # nft --debug=netlink insert rule inet x y 'goto { accept; }'
> | inet (null) (null) use 0
# nft add table x
# nft --debug=netlink add chain x y
ip (null) (null) use 0
table is null, at least this one should be set on, but this is
a partially different issue.
> | inet x
> | [ immediate reg 0 accept ]
> |
> | inet x y
> | [ immediate reg 0 goto ]
> | [...]
>
> Thanks, Phil
