On Wed, Sep 12, 2018 at 5:33 PM, Stephen Hemminger
<step...@networkplumber.org> wrote:
>
> On Wed, 12 Sep 2018 16:29:28 -0700
> Mahesh Bandewar <mah...@bandewar.net> wrote:
>
> > From: Mahesh Bandewar <mahe...@google.com>
> >
> > A local program using iproute2 lib pointed out the issue and looking
> > at the code it is pretty obvious -
> >
> > a = (struct nlmsghdr *)b;
> > ...
> > free(b);
> > if (a->nlmsg_seq == seq)
> > ...
> >
> > Fixes: 86bf43c7c2fd ("lib/libnetlink: update rtnl_talk to support malloc
> > buff at run time")
> > Signed-off-by: Mahesh Bandewar <mahe...@google.com>
>
> Yes, this is a real problem.
>
> Maybe a minimal patch like this would be enough:
actually that will leave the memory leak at the 'goto next' line (just
few lines below) since that jump will overwrite the buf.
> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
> index 928de1dd16d8..ab2d8452e4a1 100644
> --- a/lib/libnetlink.c
> +++ b/lib/libnetlink.c
> @@ -661,6 +661,8 @@ next:
> if (l < sizeof(struct nlmsgerr)) {
> fprintf(stderr, "ERROR truncated\n");
> } else if (!err->error) {
> + __u32 err_seq = h->nlmsg_seq;
> +
> /* check messages from kernel */
> nl_dump_ext_ack(h, errfn);
>
> @@ -668,7 +670,8 @@ next:
> *answer = (struct nlmsghdr
> *)buf;
> else
> free(buf);
> - if (h->nlmsg_seq == seq)
> +
> + if (err_seq == seq)
> return 0;
> else if (i < iovlen)
> goto next;
>
