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dlsym: fix the race when snd_libdir_origin is freed

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snd_dlobj_cache_cleanup() function frees snd_libdir_origin, but
the pointer may be used again in snd_dlpath().

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1847508
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
This commit is contained in:
Jaroslav Kysela 2020-06-18 08:41:02 +02:00
parent 58682bedb6
commit 20e003a63d
1 changed files with 25 additions and 12 deletions
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37
src/dlmisc.c
View file

@ -34,14 +34,21 @@
#endif #endif
#include <limits.h> #include <limits.h>
#if defined(HAVE_LIBDL) && defined(__GLIBC__) && !defined(__UCLIBC__)
#define DL_ORIGIN_AVAILABLE 1
#endif
#ifndef DOC_HIDDEN #ifndef DOC_HIDDEN
#ifndef PIC #ifndef PIC
struct snd_dlsym_link *snd_dlsym_start = NULL; struct snd_dlsym_link *snd_dlsym_start = NULL;
#endif #endif
#ifdef DL_ORIGIN_AVAILABLE
static int snd_libdir_plugin_dir_set = 0;
static char *snd_libdir_origin = NULL; static char *snd_libdir_origin = NULL;
#endif #endif
#endif
#ifdef HAVE_LIBPTHREAD #if defined(DL_ORIGIN_AVAILABLE) && defined(HAVE_LIBPTHREAD)
static pthread_mutex_t snd_dlpath_mutex = PTHREAD_MUTEX_INITIALIZER; static pthread_mutex_t snd_dlpath_mutex = PTHREAD_MUTEX_INITIALIZER;
static inline void snd_dlpath_lock(void) static inline void snd_dlpath_lock(void)
@ -68,11 +75,9 @@ static inline void snd_dlpath_unlock(void) {}
*/ */
int snd_dlpath(char *path, size_t path_len, const char *name) int snd_dlpath(char *path, size_t path_len, const char *name)
{ {
#ifdef HAVE_LIBDL #ifdef DL_ORIGIN_AVAILABLE
#if defined(__GLIBC__) && !defined(__UCLIBC__)
static int plugin_dir_set = 0;
snd_dlpath_lock(); snd_dlpath_lock();
if (!plugin_dir_set) { if (!snd_libdir_plugin_dir_set) {
struct link_map *links; struct link_map *links;
Dl_info info; Dl_info info;
char origin[PATH_MAX]; char origin[PATH_MAX];
@ -83,15 +88,17 @@ int snd_dlpath(char *path, size_t path_len, const char *name)
if (access(path, X_OK) == 0) if (access(path, X_OK) == 0)
snd_libdir_origin = strdup(origin); snd_libdir_origin = strdup(origin);
} }
plugin_dir_set = 1; snd_libdir_plugin_dir_set = 1;
}
if (snd_libdir_origin) {
snprintf(path, path_len, "%s/alsa-lib/%s", snd_libdir_origin, name);
} else {
snprintf(path, path_len, "%s/%s", ALSA_PLUGIN_DIR, name);
} }
snd_dlpath_unlock(); snd_dlpath_unlock();
#else
snprintf(path, path_len, "%s/%s", ALSA_PLUGIN_DIR, name);
#endif #endif
#endif
if (snd_libdir_origin)
snprintf(path, path_len, "%s/alsa-lib/%s", snd_libdir_origin, name);
else
snprintf(path, path_len, "%s/%s", ALSA_PLUGIN_DIR, name);
return 0; return 0;
} }
@ -440,7 +447,13 @@ void snd_dlobj_cache_cleanup(void)
free((void *)c->lib); /* shut up gcc warning */ free((void *)c->lib); /* shut up gcc warning */
free(c); free(c);
} }
free(snd_libdir_origin);
snd_dlobj_unlock(); snd_dlobj_unlock();
#ifdef DL_ORIGIN_AVAILABLE
snd_dlpath_lock();
snd_libdir_plugin_dir_set = 0;
free(snd_libdir_origin);
snd_libdir_origin = NULL;
snd_dlpath_unlock();
#endif
} }
#endif #endif