[Bug 202636] race in lib/libc/nls/msgcat.c
bugzilla-noreply at freebsd.org
bugzilla-noreply at freebsd.org
Tue Aug 25 03:21:04 UTC 2015
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=202636
Bug ID: 202636
Summary: race in lib/libc/nls/msgcat.c
Product: Base System
Version: 11.0-CURRENT
Hardware: Any
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: threads
Assignee: freebsd-threads at FreeBSD.org
Reporter: henry.hu.sh at gmail.com
Tracing from crashing xfdesktop, I found that the following program crashes in
seconds (in environment, set LANG=zh_CN.UTF-8):
#include <nl_types.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <locale.h>
#include <pthread.h>
void* work(void *arg) {
while (1) {
nl_catd catd = catopen("libc", NL_CAT_LOCALE);
catgets(catd, 1, 2, "No such file or directory");
catclose(catd);
}
}
int main() {
setlocale(LC_MESSAGES, "");
pthread_t thr1, thr2, thr3, thr4;
pthread_create(&thr1, NULL, &work, NULL);
pthread_create(&thr2, NULL, &work, NULL);
pthread_create(&thr3, NULL, &work, NULL);
pthread_create(&thr4, NULL, &work, NULL);
pthread_join(thr1, NULL);
pthread_join(thr2, NULL);
pthread_join(thr3, NULL);
pthread_join(thr4, NULL);
}
It always crashes somewhere in catgets:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 801016000 (LWP 101899/test)]
catgets (catd=0x801615170, set_id=1, msg_id=2, s=0x400a9b "No such file or
directory") at /usr/src/lib/libc/nls/msgcat.c:280
280 u = ntohl((u_int32_t)cat_hdr->__nsets) - 1;
and it looks like that catd is freed:
(gdb) p *catd
$2 = {__data = 0x5a5a5a5a5a5a5a5a, __size = 1515870810}
After a closer look, it looks like that the increments to np->refcount is racy.
See https://svnweb.freebsd.org/base/head/lib/libc/nls/msgcat.c?annotate=278530.
It is only protected by a read lock, so multiple threads may change the
refcount at the same time, thus it is a race condition and may corrupt the
refcount field.
Proposed fix:
Index: lib/libc/nls/msgcat.c
===================================================================
--- lib/libc/nls/msgcat.c (版本 287028)
+++ lib/libc/nls/msgcat.c (工作副本)
@@ -141,7 +141,7 @@
}
/* Try to get it from the cache first */
- RLOCK(NLERR);
+ WLOCK(NLERR);
SLIST_FOREACH(np, &cache, list) {
if ((strcmp(np->name, name) == 0) &&
((lang != NULL && np->lang != NULL &&
@@ -376,7 +376,7 @@
* One more try in cache; if it was not found by name,
* it might still be found by absolute path.
*/
- RLOCK(NLERR);
+ WLOCK(NLERR);
SLIST_FOREACH(np, &cache, list) {
if ((np->path != NULL) && (strcmp(np->path, path) == 0)) {
np->refcount++;
This patch fixes the case in catopen().
This also changes the access in load_msgcat(), which also seems to be
incorrect.
--
You are receiving this mail because:
You are the assignee for the bug.
More information about the freebsd-threads
mailing list