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pimd: harden MLD code loop boundaries

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Coverity complains about these being tainted/untrusted loop boundaries.
The way the code works, it's counting up groups/sources, but keeps
checking against remaining data length in the packet - which is
perfectly fine IMHO.  Except Coverity doesn't understand it :(

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
This commit is contained in:
David Lamparter 2023-04-21 15:14:43 +02:00
parent 4dbef8567b
commit ac4304d0fa
1 changed files with 25 additions and 8 deletions
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33
pimd/pim6_mld.c
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@ -594,7 +594,7 @@ static void gm_sg_expiry_cancel(struct gm_sg *sg)
* everything else is thrown into pkt for creation of state in pass 2 * everything else is thrown into pkt for creation of state in pass 2
*/ */
static void gm_handle_v2_pass1(struct gm_packet_state *pkt, static void gm_handle_v2_pass1(struct gm_packet_state *pkt,
struct mld_v2_rec_hdr *rechdr) struct mld_v2_rec_hdr *rechdr, size_t n_src)
{ {
/* NB: pkt->subscriber can be NULL here if the subscriber was not /* NB: pkt->subscriber can be NULL here if the subscriber was not
* previously seen! * previously seen!
@ -603,7 +603,6 @@ static void gm_handle_v2_pass1(struct gm_packet_state *pkt,
struct gm_sg *grp; struct gm_sg *grp;
struct gm_packet_sg *old_grp = NULL; struct gm_packet_sg *old_grp = NULL;
struct gm_packet_sg *item; struct gm_packet_sg *item;
size_t n_src = ntohs(rechdr->n_src);
size_t j; size_t j;
bool is_excl = false; bool is_excl = false;
@ -816,13 +815,24 @@ static void gm_handle_v2_report(struct gm_if *gm_ifp,
return; return;
} }
/* errors after this may at least partially process the packet */
gm_ifp->stats.rx_new_report++;
hdr = (struct mld_v2_report_hdr *)data; hdr = (struct mld_v2_report_hdr *)data;
data += sizeof(*hdr); data += sizeof(*hdr);
len -= sizeof(*hdr); len -= sizeof(*hdr);
n_records = ntohs(hdr->n_records);
if (n_records > len / sizeof(struct mld_v2_rec_hdr)) {
/* note this is only an upper bound, records with source lists
* are larger. This is mostly here to make coverity happy.
*/
zlog_warn(log_pkt_src(
"malformed MLDv2 report (infeasible record count)"));
gm_ifp->stats.rx_drop_malformed++;
return;
}
/* errors after this may at least partially process the packet */
gm_ifp->stats.rx_new_report++;
/* can't have more *,G and S,G items than there is space for ipv6 /* can't have more *,G and S,G items than there is space for ipv6
* addresses, so just use this to allocate temporary buffer * addresses, so just use this to allocate temporary buffer
*/ */
@ -833,8 +843,6 @@ static void gm_handle_v2_report(struct gm_if *gm_ifp,
pkt->iface = gm_ifp; pkt->iface = gm_ifp;
pkt->subscriber = gm_subscriber_findref(gm_ifp, pkt_src->sin6_addr); pkt->subscriber = gm_subscriber_findref(gm_ifp, pkt_src->sin6_addr);
n_records = ntohs(hdr->n_records);
/* validate & remove state in v2_pass1() */ /* validate & remove state in v2_pass1() */
for (i = 0; i < n_records; i++) { for (i = 0; i < n_records; i++) {
struct mld_v2_rec_hdr *rechdr; struct mld_v2_rec_hdr *rechdr;
@ -872,7 +880,7 @@ static void gm_handle_v2_report(struct gm_if *gm_ifp,
data += record_size; data += record_size;
len -= record_size; len -= record_size;
gm_handle_v2_pass1(pkt, rechdr); gm_handle_v2_pass1(pkt, rechdr, n_src);
} }
if (!pkt->n_active) { if (!pkt->n_active) {
@ -1496,6 +1504,15 @@ static void gm_handle_query(struct gm_if *gm_ifp,
gm_handle_q_group(gm_ifp, &timers, hdr->grp); gm_handle_q_group(gm_ifp, &timers, hdr->grp);
gm_ifp->stats.rx_query_new_group++; gm_ifp->stats.rx_query_new_group++;
} else { } else {
/* this is checked above:
* if (len >= sizeof(struct mld_v2_query_hdr)) {
* size_t src_space = ntohs(hdr->n_src) * sizeof(pim_addr);
* if (len < sizeof(struct mld_v2_query_hdr) + src_space) {
*/
assume(ntohs(hdr->n_src) <=
(len - sizeof(struct mld_v2_query_hdr)) /
sizeof(pim_addr));
gm_handle_q_groupsrc(gm_ifp, &timers, hdr->grp, hdr->srcs, gm_handle_q_groupsrc(gm_ifp, &timers, hdr->grp, hdr->srcs,
ntohs(hdr->n_src)); ntohs(hdr->n_src));
gm_ifp->stats.rx_query_new_groupsrc++; gm_ifp->stats.rx_query_new_groupsrc++;