sss_client: Use unique lock for memory cache

Previously the sma lock was used as for communication with
responder. However it would cause a deadlock in case of
re-checking memcache after acquiring the lock and before communication with
responder..

Required by:
https://fedorahosted.org/sssd/ticket/2581

Reviewed-by: Michal Židek <mzidek@redhat.com>

3 files changed, 26 insertions, 4 deletions

diff --git a/src/sss_client/common.c b/src/sss_client/common.c
index 383572bad..970cfe6f3 100644
--- a/src/sss_client/common.c
+++ b/src/sss_client/common.c
@@ -1032,6 +1032,7 @@ struct sss_mutex {
 
 static void sss_nss_mt_init(void);
 static void sss_pam_mt_init(void);
+static void sss_nss_mc_mt_init(void);
 
 static struct sss_mutex sss_nss_mtx = { .mtx  = PTHREAD_MUTEX_INITIALIZER,
                                         .once = PTHREAD_ONCE_INIT,
@@ -1041,6 +1042,9 @@ static struct sss_mutex sss_pam_mtx = { .mtx  = PTHREAD_MUTEX_INITIALIZER,
                                         .once = PTHREAD_ONCE_INIT,
                                         .init = sss_pam_mt_init };
 
+static struct sss_mutex sss_nss_mc_mtx = { .mtx  = PTHREAD_MUTEX_INITIALIZER,
+                                           .once = PTHREAD_ONCE_INIT,
+                                           .init = sss_nss_mc_mt_init };
 
 /* Wrappers for robust mutex support */
 static int sss_mutexattr_setrobust (pthread_mutexattr_t *attr)
@@ -1125,6 +1129,20 @@ void sss_pam_unlock(void)
     sss_mt_unlock(&sss_pam_mtx);
 }
 
+/* NSS mutex wrappers */
+static void sss_nss_mc_mt_init(void)
+{
+    sss_mt_init(&sss_nss_mc_mtx);
+}
+void sss_nss_mc_lock(void)
+{
+    sss_mt_lock(&sss_nss_mc_mtx);
+}
+void sss_nss_mc_unlock(void)
+{
+    sss_mt_unlock(&sss_nss_mc_mtx);
+}
+
 #else
 
 /* sorry no mutexes available */
@@ -1132,6 +1150,8 @@ void sss_nss_lock(void) { return; }
 void sss_nss_unlock(void) { return; }
 void sss_pam_lock(void) { return; }
 void sss_pam_unlock(void) { return; }
+void sss_nss_mc_lock(void) { return; }
+void sss_nss_mc_unlock(void) { return; }
 #endif
 
 
diff --git a/src/sss_client/nss_mc_common.c b/src/sss_client/nss_mc_common.c
index 89ff6b46e..707d1249f 100644
--- a/src/sss_client/nss_mc_common.c
+++ b/src/sss_client/nss_mc_common.c
@@ -121,7 +121,7 @@ static errno_t sss_nss_mc_init_ctx(const char *name,
     char *file = NULL;
     int ret;
 
-    sss_nss_lock();
+    sss_nss_mc_lock();
     /* check if ctx is initialised by previous thread. */
     if (ctx->initialized != UNINITIALIZED) {
         ret = sss_nss_check_header(ctx);
@@ -172,7 +172,7 @@ done:
         sss_nss_mc_destroy_ctx(ctx);
     }
     free(file);
-    sss_nss_unlock();
+    sss_nss_mc_unlock();
 
     return ret;
 }
@@ -217,11 +217,11 @@ errno_t sss_nss_mc_get_ctx(const char *name, struct sss_cli_mc_ctx *ctx)
         }
         if (ctx->initialized == RECYCLED && ctx->active_threads == 0) {
             /* just one thread should call munmap */
-            sss_nss_lock();
+            sss_nss_mc_lock();
             if (ctx->initialized == RECYCLED) {
                 sss_nss_mc_destroy_ctx(ctx);
             }
-            sss_nss_unlock();
+            sss_nss_mc_unlock();
         }
         if (need_decrement) {
             /* In case of error, we will not touch mmapped area => decrement */
diff --git a/src/sss_client/sss_cli.h b/src/sss_client/sss_cli.h
index 6902d711e..0dfb525ba 100644
--- a/src/sss_client/sss_cli.h
+++ b/src/sss_client/sss_cli.h
@@ -594,6 +594,8 @@ void sss_nss_lock(void);
 void sss_nss_unlock(void);
 void sss_pam_lock(void);
 void sss_pam_unlock(void);
+void sss_nss_mc_lock(void);
+void sss_nss_mc_unlock(void);
 
 errno_t sss_readrep_copy_string(const char *in,
                                 size_t *offset,