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Fix widespread off-by-one error dealing with port numbers

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Port numbers (for both TCP and UDP) are 16-bit, and so fit exactly into a
'short'.  USHRT_MAX is therefore the maximum port number and this is widely
used in the code.  Unfortunately, a lot of those places don't actually
want the maximum port number (USHRT_MAX == 65535), they want the total
number of ports (65536).  This leads to a number of potentially nasty
consequences:

 * We have buffer overruns on the port_fwd::delta array if we try to use
   port 65535
 * We have similar potential overruns for the tcp_sock_* arrays
 * Interestingly udp_act had the correct size, but we can calculate it in
   a more direct manner
 * We have a logical overrun of the ports bitmap as well, although it will
   just use an unused bit in the last byte so isnt harmful
 * Many loops don't consider port 65535 (which does mitigate some but not
   all of the buffer overruns above)
 * In udp_invert_portmap() we incorrectly compute the reverse port
   translation for return packets

Correct all these by using a new NUM_PORTS defined explicitly for this
purpose.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
David Gibson 2022-09-24 19:08:22 +10:00 • committed by Stefano Brivio
parent 3ede07aac9
commit d5b80ccc72
5 changed files with 19 additions and 16 deletions

12
tcp.c
View file

@ -547,9 +547,9 @@ static const char *tcp_flag_str[] __attribute((__unused__)) = {
};
/* Listening sockets, used for automatic port forwarding in pasta mode only */
static int tcp_sock_init_lo [USHRT_MAX][IP_VERSIONS];
static int tcp_sock_init_ext [USHRT_MAX][IP_VERSIONS];
static int tcp_sock_ns [USHRT_MAX][IP_VERSIONS];
static int tcp_sock_init_lo [NUM_PORTS][IP_VERSIONS];
static int tcp_sock_init_ext [NUM_PORTS][IP_VERSIONS];
static int tcp_sock_ns [NUM_PORTS][IP_VERSIONS];
/* Table of destinations with very low RTT (assumed to be local), LRU */
static struct in6_addr low_rtt_dst[LOW_RTT_TABLE_SIZE];
@ -3186,7 +3186,7 @@ static int tcp_sock_init_ns(void *arg)
ns_enter(c);
for (port = 0; port < USHRT_MAX; port++) {
for (port = 0; port < NUM_PORTS; port++) {
if (!bitmap_isset(c->tcp.fwd_out.map, port))
continue;
@ -3386,7 +3386,7 @@ static int tcp_port_rebind(void *arg)
if (a->bind_in_ns) {
ns_enter(a->c);
for (port = 0; port < USHRT_MAX; port++) {
for (port = 0; port < NUM_PORTS; port++) {
if (!bitmap_isset(a->c->tcp.fwd_out.map, port)) {
if (tcp_sock_ns[port][V4] >= 0) {
close(tcp_sock_ns[port][V4]);
@ -3410,7 +3410,7 @@ static int tcp_port_rebind(void *arg)
tcp_sock_init(a->c, 1, AF_UNSPEC, NULL, port);
}
} else {
for (port = 0; port < USHRT_MAX; port++) {
for (port = 0; port < NUM_PORTS; port++) {
if (!bitmap_isset(a->c->tcp.fwd_in.map, port)) {
if (tcp_sock_init_ext[port][V4] >= 0) {
close(tcp_sock_init_ext[port][V4]);