Re: [PATCH 1/2] bpf: sockmap, fix uninitialized variable

[Gustavo A. R. Silva]

Hi John,

On 05/17/2018 12:27 PM, John Fastabend wrote:
> On 05/17/2018 07:08 AM, Gustavo A. R. Silva wrote:
> > There is a potential execution path in which variable err is
> > returned without being properly initialized previously.
> >
> > Fix this by initializing variable err to 0.
> >
> > Addresses-Coverity-ID: 1468964 ("Uninitialized scalar variable")
> > Fixes: e5cd3abcb31a ("bpf: sockmap, refactor sockmap routines to work
> > with hashmap")
> > Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
> > ---
> >   kernel/bpf/sockmap.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
> > index c6de139..41b41fc 100644
> > --- a/kernel/bpf/sockmap.c
> > +++ b/kernel/bpf/sockmap.c
> > @@ -1713,7 +1713,7 @@ static int __sock_map_ctx_update_elem(struct bpf_map *map,
> >   	struct smap_psock_map_entry *e = NULL;
> >   	struct smap_psock *psock;
> >   	bool new = false;
> > -	int err;
> > +	int err = 0;
> >   
> >   	/* 1. If sock map has BPF programs those will be inherited by the
> >   	 * sock being added. If the sock is already attached to BPF programs
>
> Thanks for catching this and the quick fix. The path to hit this case
> is to add a sock to a map (without a BPF program) where the sock already
> has been added to another map. I don't have any tests for the case with
> socks in multiple maps so I'll add some to the selftests so I remember
> this case.

Glad to help. :)

> The alternative fix would be to always 'return 0' at the end of the
> function, but I think its probably better to init err here like above.

Yeah. I think initializing err is better in this case.

> Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>

Thank you
--
Gustavo