On Thu, Jun 23, 2016 at 10:49:53AM +0000, Fabien Siron wrote:
> Quoting Dmitry V. Levin (2016-06-22 17:40:39)
> > On Wed, Jun 22, 2016 at 01:27:06PM +0000, Fabien Siron wrote:
> [...]
> > > +static int
> > > +nlmsg_fetch(struct tcb *tcp, struct nlmsghdr *nlmsghdr, unsigned long
> > > addr,
> > > + unsigned long len) {
> > > + if (len < sizeof(struct nlmsghdr)) {
> > > + if (len != 0)
> > > + printstr(tcp, addr, len);
> > > + return 0;
> > > + }
> > > +
> > > + if (umove_or_printaddr(tcp, addr, nlmsghdr) == -1)
> > > + return 0;
> > > +
> > > + if (len < nlmsghdr->nlmsg_len) {
> > > + printstr(tcp, addr, len);
> > > + return 0;
> > > + }
> >
> > I think that if struct nlmsghdr has been successfully fetched,
> > the header should be printed regardless of its nlmsg_len.
>
> So you actually want to remove the last test?
Yes, and rename this function to fetch_nlmsghdr.
> > > + return 1;
> > > +}
> > >
> > > +static unsigned long
> > > +nlmsg_next(struct nlmsghdr *nlmsghdr, unsigned long addr, unsigned long
> > > *len) {
Ditto, next_nlmsghdr.
> > > + if (NLMSG_ALIGN(nlmsghdr->nlmsg_len) == 0 ||
> > > + NLMSG_ALIGN(nlmsghdr->nlmsg_len) > *len)
> > > + return 0;
> >
> > This is not going to happen with current implementation of nlmsg_fetch,
> > but if nlmsg_fetch changes and if this condition is true, then
> > *len remains unchanged and the subsequent nlmsg_fetch prints NULL.
>
> A way to fix that is to put *len to 0 in this test. But the problem is that
> nothing will be printed if sizeof(struct nlmsghdr) < *len <
> nlmsghdr->nlmsg_len.
It's up to decode_netlink_msg to decide how to print such messages.
decode_netlink has to be consistent. Every successfully fetched struct
nlmsghdr should be printed. When decode_netlink leaves some bytes of the
message undecoded, it has to print an indication.
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