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Don't read from a disarmed or invalid timerfd

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Numerous isues have been reported for deadlocks that are caused by
a blocking read in res_timing_timerfd on a file descriptor that will
never be written to. This patch adds some checks to make sure that
the timerfd is both valid and armed before calling read().

Should fix: ASTERISK-18142, ASTERISK-18197, ASTERISK-18166, AST-486
AST-495, AST-507 and possibly others.

Review: https://reviewboard.asterisk.org/r/1361/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@332320 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Terry Wilson
2011-08-17 17:35:27 +00:00
parent 9328590ddb
commit a9db588064
1 changed files with 27 additions and 0 deletions
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27
res/res_timing_timerfd.c
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@@ -162,8 +162,32 @@ static void timerfd_timer_ack(int handle, unsigned int quantity)
{ {
uint64_t expirations; uint64_t expirations;
int read_result = 0; int read_result = 0;
struct timerfd_timer *our_timer, find_helper = {
.handle = handle,
};
if (!(our_timer = ao2_find(timerfd_timers, &find_helper, OBJ_POINTER))) {
ast_log(LOG_ERROR, "Couldn't find a timer with handle %d\n", handle);
return;
}
ao2_lock(our_timer);
do { do {
struct itimerspec timer_status;
if (timerfd_gettime(handle, &timer_status)) {
ast_log(LOG_ERROR, "Call to timerfd_gettime() error: %s\n", strerror(errno));
expirations = 0;
break;
}
if (timer_status.it_value.tv_sec == 0 && timer_status.it_value.tv_nsec == 0) {
ast_debug(1, "Avoiding read on disarmed timerfd %d\n", handle);
expirations = 0;
break;
}
read_result = read(handle, &expirations, sizeof(expirations)); read_result = read(handle, &expirations, sizeof(expirations));
if (read_result == -1) { if (read_result == -1) {
if (errno == EINTR || errno == EAGAIN) { if (errno == EINTR || errno == EAGAIN) {
@@ -175,6 +199,9 @@ static void timerfd_timer_ack(int handle, unsigned int quantity)
} }
} while (read_result != sizeof(expirations)); } while (read_result != sizeof(expirations));
ao2_unlock(our_timer);
ao2_ref(our_timer, -1);
if (expirations != quantity) { if (expirations != quantity) {
ast_debug(2, "Expected to acknowledge %u ticks but got %llu instead\n", quantity, (unsigned long long) expirations); ast_debug(2, "Expected to acknowledge %u ticks but got %llu instead\n", quantity, (unsigned long long) expirations);
} }