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Avoid an overflow when computing the staleness.

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This issue was found by running libfuzz on the userland stack.

MFC after:	1 week
This commit is contained in:
Michael Tuexen 2017-09-19 20:09:58 +00:00
parent 3cabd93e26
commit 564a95f485
1 changed files with 15 additions and 11 deletions
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26
sys/netinet/sctp_input.c
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@ -2553,15 +2553,12 @@ sctp_handle_cookie_echo(struct mbuf *m, int iphlen, int offset,
/* Expire time is in Ticks, so we convert to seconds */
time_expires.tv_sec = cookie->time_entered.tv_sec + TICKS_TO_SEC(cookie->cookie_life);
time_expires.tv_usec = cookie->time_entered.tv_usec;
/*
* TODO sctp_constants.h needs alternative time macros when _KERNEL
* is undefined.
*/
if (timevalcmp(&now, &time_expires, >)) {
/* cookie is stale! */
struct mbuf *op_err;
struct sctp_error_stale_cookie *cause;
uint32_t tim;
struct timeval diff;
uint32_t staleness;
op_err = sctp_get_mbuf_for_msg(sizeof(struct sctp_error_stale_cookie),
0, M_NOWAIT, 1, MT_DATA);
@ -2575,12 +2572,19 @@ sctp_handle_cookie_echo(struct mbuf *m, int iphlen, int offset,
cause->cause.code = htons(SCTP_CAUSE_STALE_COOKIE);
cause->cause.length = htons((sizeof(struct sctp_paramhdr) +
(sizeof(uint32_t))));
/* seconds to usec */
tim = (now.tv_sec - time_expires.tv_sec) * 1000000;
/* add in usec */
if (tim == 0)
tim = now.tv_usec - cookie->time_entered.tv_usec;
cause->stale_time = htonl(tim);
diff = now;
timevalsub(&diff, &time_expires);
if (diff.tv_sec > UINT32_MAX / 1000000) {
staleness = UINT32_MAX;
} else {
staleness = diff.tv_sec * 1000000;
}
if (UINT32_MAX - staleness >= diff.tv_usec) {
staleness += diff.tv_usec;
} else {
staleness = UINT32_MAX;
}
cause->stale_time = htonl(staleness);
sctp_send_operr_to(src, dst, sh, cookie->peers_vtag, op_err,
mflowtype, mflowid, l_inp->fibnum,
vrf_id, port);