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<p>Hello Daniel,</p>
<p>thanks for the notice of the buffer length - will fix it and test again.</p>
<p>The report from the tool mentioned that it is an issue also for multi-process, but of course more critical for multi-threaded:<br>
</p>
<p>"The time related functions such as <code>gmtime</code> fill data into a <code>
tm</code> struct or <code>char</code> array in shared memory and then returns a pointer to that memory. If the function is called from multiple places in the same program, and especially if it is called from multiple threads in the same program, then the calls
will overwrite each other's data."</p>
<p>Therefore I think that it is definitely safer, especially as there might be libraries that use it as well, that we don't see.</p>
<p>We probably don't need to backport it, thought.<br>
</p>
<p>Cheers,</p>
<p>Henning<br>
</p>
<div class="moz-cite-prefix">Am 20.09.19 um 11:03 schrieb Daniel-Constantin Mierla:<br>
</div>
<blockquote type="cite" cite="mid:6f6012f8-123d-b186-07f3-0c366e3cc35b@gmail.com">
<pre class="moz-quote-pre" wrap="">Hello,
were these changes to use ctime_r() (and in other commits gmtime_r(),
localtime_r(), asctime_r()) required to fix existing issues or more like
a preference to use them? Because Kamailio is multiprocess and thread
safety should not be a concern, otherwise there might be a lot of other
place to take care of thread safety...
Anyhow, there are out of bound writes introduced as the buffers must be
at least 26 chars long, not 25 -- those need to be fixed.
Cheers,
Daniel
On 20.09.19 00:04, Henning Westerholt wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Module: kamailio
Branch: master
Commit: dc2acb895538131e99c770da6f7448cb5a46fc32
URL: <a class="moz-txt-link-freetext" href="https://github.com/kamailio/kamailio/commit/dc2acb895538131e99c770da6f7448cb5a46fc32">https://github.com/kamailio/kamailio/commit/dc2acb895538131e99c770da6f7448cb5a46fc32</a>
Author: Henning Westerholt <a class="moz-txt-link-rfc2396E" href="mailto:hw@skalatan.de"><hw@skalatan.de></a>
Committer: Henning Westerholt <a class="moz-txt-link-rfc2396E" href="mailto:hw@skalatan.de"><hw@skalatan.de></a>
Date: 2019-09-19T23:49:32+02:00
core: replace glibc time function calls with the thread-safe versions
- replace glibc time function calls with the thread-safe versions, to prevent
race conditions from multi-process / multi-threaded access
- used in 'kamcmd core.uptime' rpc cmd, no functional change, locally tested
---
Modified: src/core/core_cmd.c
---
Diff: <a class="moz-txt-link-freetext" href="https://github.com/kamailio/kamailio/commit/dc2acb895538131e99c770da6f7448cb5a46fc32.diff">https://github.com/kamailio/kamailio/commit/dc2acb895538131e99c770da6f7448cb5a46fc32.diff</a>
Patch: <a class="moz-txt-link-freetext" href="https://github.com/kamailio/kamailio/commit/dc2acb895538131e99c770da6f7448cb5a46fc32.patch">https://github.com/kamailio/kamailio/commit/dc2acb895538131e99c770da6f7448cb5a46fc32.patch</a>
---
diff --git a/src/core/core_cmd.c b/src/core/core_cmd.c
index 5b1c4624ed..717e240fde 100644
--- a/src/core/core_cmd.c
+++ b/src/core/core_cmd.c
@@ -224,8 +224,7 @@ static const char* dst_blst_stats_get_doc[] = {
#endif
-
-#define MAX_CTIME_LEN 128
+#define MAX_CTIME_LEN 25
/* up time */
static char up_since_ctime[MAX_CTIME_LEN];
@@ -381,13 +380,14 @@ static void core_uptime(rpc_t* rpc, void* c)
{
void* s;
time_t now;
+ char buf[MAX_CTIME_LEN];
str snow;
+ snow.s = buf;
time(&now);
if (rpc->add(c, "{", &s) < 0) return;
- snow.s = ctime(&now);
- if(snow.s) {
+ if(ctime_r(&now, snow.s)) {
snow.len = strlen(snow.s);
if(snow.len>2 && snow.s[snow.len-1]=='\n') snow.len--;
rpc->struct_add(s, "S", "now", &snow);
@@ -1187,21 +1187,14 @@ int register_core_rpcs(void)
int rpc_init_time(void)
{
- char *t;
- t=ctime(&up_since);
- if (strlen(t)+1>=MAX_CTIME_LEN) {
- ERR("Too long data %d\n", (int)strlen(t));
+ char t[MAX_CTIME_LEN];
+ int len;
+ if (! ctime_r(&up_since, t)) {
+ ERR("Invalid time value\n");
return -1;
}
strcpy(up_since_ctime, t);
- t = up_since_ctime + strlen(up_since_ctime);
- while(t>up_since_ctime) {
- if(*t=='\0' || *t=='\r' || *t=='\n') {
- *t = '\0';
- } else {
- break;
- }
- t--;
- }
+ len = strlen(up_since_ctime);
+ if(len>2 && up_since_ctime[len-1]=='\n') up_since_ctime[len-1]='\0';
return 0;
}
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</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
</pre>
</blockquote>
<pre class="moz-signature" cols="72">--
Kamailio Merchandising - <a class="moz-txt-link-freetext" href="https://skalatan.de/merchandising/">https://skalatan.de/merchandising/</a>
Kamailio services - <a class="moz-txt-link-freetext" href="https://skalatan.de/services">https://skalatan.de/services</a>
Henning Westerholt - <a class="moz-txt-link-freetext" href="https://skalatan.de/blog/">https://skalatan.de/blog/</a></pre>
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