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Fix doubly call of dlclose() in dlobj caching code

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When multiple dlobj_cache items point to the same dlobj, dlclose() may
be called wrongly multiple times when these items are cleared, because
we manage the dlobj_cache list as a flat list.  This results in a bad
segfault we've seen in openal-soft, for example.

For fixing this, we need the refcounting of dlobj itself.  But, in
this case, we don't have to manage yet another list,  since dlopen()
does a proper refcounting by itself.  That is, we can just call always
dlopen() at each time a new function is assigned, and also call
dlclose() for each released dlobj_cache item at cleanup.

Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=814250

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2013-04-15 18:12:17 +02:00
parent 812e4b0c5b
commit e1e40c2553
1 changed files with 11 additions and 20 deletions
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31
src/dlmisc.c
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@ -208,8 +208,7 @@ void *snd_dlobj_cache_get(const char *lib, const char *name,
{ {
struct list_head *p; struct list_head *p;
struct dlobj_cache *c; struct dlobj_cache *c;
void *func, *dlobj = NULL; void *func, *dlobj;
int dlobj_close = 0;
snd_dlobj_lock(); snd_dlobj_lock();
list_for_each(p, &pcm_dlobj_list) { list_for_each(p, &pcm_dlobj_list) {
@ -220,7 +219,6 @@ void *snd_dlobj_cache_get(const char *lib, const char *name,
continue; continue;
if (!lib && c->lib) if (!lib && c->lib)
continue; continue;
dlobj = c->dlobj;
if (strcmp(c->name, name) == 0) { if (strcmp(c->name, name) == 0) {
c->refcnt++; c->refcnt++;
func = c->func; func = c->func;
@ -228,17 +226,16 @@ void *snd_dlobj_cache_get(const char *lib, const char *name,
return func; return func;
} }
} }
dlobj = snd_dlopen(lib, RTLD_NOW);
if (dlobj == NULL) { if (dlobj == NULL) {
dlobj = snd_dlopen(lib, RTLD_NOW); if (verbose)
if (dlobj == NULL) { SNDERR("Cannot open shared library %s",
if (verbose)
SNDERR("Cannot open shared library %s",
lib ? lib : "[builtin]"); lib ? lib : "[builtin]");
snd_dlobj_unlock(); snd_dlobj_unlock();
return NULL; return NULL;
}
dlobj_close = 1;
} }
func = snd_dlsym(dlobj, name, version); func = snd_dlsym(dlobj, name, version);
if (func == NULL) { if (func == NULL) {
if (verbose) if (verbose)
@ -257,8 +254,7 @@ void *snd_dlobj_cache_get(const char *lib, const char *name,
free((void *)c->lib); free((void *)c->lib);
free(c); free(c);
__err: __err:
if (dlobj_close) snd_dlclose(dlobj);
snd_dlclose(dlobj);
snd_dlobj_unlock(); snd_dlobj_unlock();
return NULL; return NULL;
} }
@ -298,16 +294,11 @@ void snd_dlobj_cache_cleanup(void)
struct list_head *p, *npos; struct list_head *p, *npos;
struct dlobj_cache *c; struct dlobj_cache *c;
/* clean up caches only when really no user is present */
snd_dlobj_lock(); snd_dlobj_lock();
list_for_each(p, &pcm_dlobj_list) {
c = list_entry(p, struct dlobj_cache, list);
if (c->refcnt)
goto unlock;
}
list_for_each_safe(p, npos, &pcm_dlobj_list) { list_for_each_safe(p, npos, &pcm_dlobj_list) {
c = list_entry(p, struct dlobj_cache, list); c = list_entry(p, struct dlobj_cache, list);
if (c->refcnt)
continue;
list_del(p); list_del(p);
snd_dlclose(c->dlobj); snd_dlclose(c->dlobj);
free((void *)c->name); /* shut up gcc warning */ free((void *)c->name); /* shut up gcc warning */