On Wed, Jun 29, 2016 at 12:20:00PM +0000, Fabien Siron wrote:
> +static unsigned long
> +next_nlmsg(struct nlmsghdr *nlmsghdr, unsigned long addr, unsigned long
> *len) {
> + if (NLMSG_ALIGN(nlmsghdr->nlmsg_len) == 0 ||
> + NLMSG_ALIGN(nlmsghdr->nlmsg_len) > *len) {
> + *len = NLMSG_ALIGN(nlmsghdr->nlmsg_len);
> + return 0;
> + }
*len may increase as result
> + *len -= NLMSG_ALIGN(nlmsghdr->nlmsg_len);
> +
> + if (addr + NLMSG_ALIGN(nlmsghdr->nlmsg_len) > addr) {
> + return addr + NLMSG_ALIGN(nlmsghdr->nlmsg_len);
> + } else {
> + *len = 0;
> + return 0;
> + }
> +}
Could it be written in a more clear and robust way? For example,
unsigned long nlmsg_len = NLMSG_ALIGN(nlmsghdr->nlmsg_len);
if (nlmsg_len < sizeof(struct nlmsghdr)) {
addr = 0;
nlmsg_len = sizeof(struct nlmsghdr);
}
if (*len >= nlmsg_len)
*len -= nlmsg_len;
else
*len = 0;
if (addr && addr + nlmsg_len > addr)
return addr + nlmsg_len;
else
return 0;
> +static void
> +decode_netlink_msg(struct tcb *tcp, struct nlmsghdr *nlmsghdr,
> + unsigned long addr, unsigned long size)
> +{
> if (size < sizeof(struct nlmsghdr)) {
> printstr(tcp, addr, size);
> return;
> }
> - if (umove_or_printaddr(tcp, addr, &nlmsghdr))
> - return;
>
> - tprintf("{{len=%u, type=", nlmsghdr.nlmsg_len);
> + tprintf("{{len=%u, type=", nlmsghdr->nlmsg_len);
>
> - printxval(netlink_types, nlmsghdr.nlmsg_type, "NLMSG_???");
> + printxval(netlink_types, nlmsghdr->nlmsg_type, "NLMSG_???");
>
> tprints(", flags=");
> - printflags(netlink_flags, nlmsghdr.nlmsg_flags, "NLM_F_???");
> + printflags(netlink_flags, nlmsghdr->nlmsg_flags, "NLM_F_???");
> /* manage get/new requests */
>
> - tprintf(", seq=%u, pid=%u}", nlmsghdr.nlmsg_seq,
> - nlmsghdr.nlmsg_pid);
> + tprintf(", seq=%u, pid=%u}", nlmsghdr->nlmsg_seq,
> + nlmsghdr->nlmsg_pid);
>
> - if (size - sizeof(struct nlmsghdr) > 0) {
> + if (nlmsghdr->nlmsg_len - sizeof(struct nlmsghdr) > 0) {
> tprints(", ");
> +
> printstr(tcp, addr + sizeof(struct nlmsghdr),
> - size - sizeof(struct nlmsghdr));
> + nlmsghdr->nlmsg_len - sizeof(struct nlmsghdr));
> }
>
> tprints("}");
> }
> +
> +void
> +decode_netlink(struct tcb *tcp, unsigned long addr, unsigned long
> total_size) {
> + struct nlmsghdr nlmsghdr;
> + unsigned long elt, size = total_size;
> + int print_array = 0;
> +
> + for (elt = 0; fetch_nlmsg(tcp, &nlmsghdr, addr, size);
> + addr = next_nlmsg(&nlmsghdr, addr, &size), elt++) {
> + if (elt == max_strlen && abbrev(tcp)) {
> + tprints("...");
> + break;
> + }
> + if (nlmsghdr.nlmsg_len < sizeof(struct nlmsghdr))
> + break;
This edition of decode_netlink will print nothing if addr == NULL,
or if the first nlmsghdr.nlmsg_len < sizeof(struct nlmsghdr).
Please add to the test all pathological cases we discussed so far.
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