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osmo-uecups
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tun_device: Avoid deadlocks logging while thread is cancelled 

We cannot garantee that LOGP will not end up calling a syscall which can
be a cancellation point. Since the syscall will be probably called while
having the logging mutex locked, an eventuall cancellation of the thread
would leave the logging mutex locked forever, hence making all other
threads deadlock as soon as they try to write anything to the log.

Change-Id: I72a0b536c8f39857960f132a5b84cdf5b8519732
This commit is contained in:
Pau Espin 2022-04-13 18:04:21 +02:00
parent f9f5b301dd
commit 7b2a729848
1 changed files with 11 additions and 0 deletions
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11
daemon/tun_device.c
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@ -139,12 +139,17 @@ static void *tun_device_thread(void *arg)
uint8_t *buffer = base_buffer + sizeof(struct gtp1_header);
struct sockaddr_storage daddr;
int old_cancelst_unused;
/* initialize the fixed part of the GTP header */
gtph->flags = 0x30;
gtph->type = GTP_TPDU;
pthread_cleanup_push(tun_device_pthread_cleanup_routine, tun);
/* IMPORTANT!: All logging functions in this function block must be called with
* PTHREAD_CANCEL_DISABLE set, otherwise the thread could be cancelled while
* holding the logging mutex, hence causing deadlock with main (or other)
* thread. */
while (1) {
struct gtp_tunnel *t;
@ -154,6 +159,7 @@ static void *tun_device_thread(void *arg)
/* 1) read from tun */
rc = read(tun->fd, buffer, MAX_UDP_PACKET);
if (rc < 0) {
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old_cancelst_unused);
LOGTUN(tun, LOGL_FATAL, "Error readingfrom tun device: %s\n", strerror(errno));
exit(1);
}
@ -162,8 +168,10 @@ static void *tun_device_thread(void *arg)
rc = parse_pkt(&pinfo, buffer, nread);
if (rc < 0) {
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old_cancelst_unused);
LOGTUN(tun, LOGL_NOTICE, "Error parsing IP packet: %s\n",
osmo_hexdump(buffer, nread));
pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &old_cancelst_unused);
continue;
}
@ -181,7 +189,9 @@ static void *tun_device_thread(void *arg)
getnameinfo((const struct sockaddr *)&pinfo.saddr,
sizeof(pinfo.saddr), host, sizeof(host), port, sizeof(port),
NI_NUMERICHOST | NI_NUMERICSERV);
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old_cancelst_unused);
LOGTUN(tun, LOGL_NOTICE, "No tunnel found for source address %s:%s\n", host, port);
pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &old_cancelst_unused);
continue;
}
outfd = t->gtp_ep->fd;
@ -193,6 +203,7 @@ static void *tun_device_thread(void *arg)
rc = sendto(outfd, base_buffer, nread+sizeof(*gtph), 0,
(struct sockaddr *)&daddr, sizeof(daddr));
if (rc < 0) {
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old_cancelst_unused);
LOGTUN(tun, LOGL_FATAL, "Error Writing to UDP socket: %s\n", strerror(errno));
exit(1);
}