libringbuffer shm: be resilient to app crash between shm_open and shm_unlink

[ust.git] / libringbuffer / shm.c

diff --git a/libringbuffer/shm.c b/libringbuffer/shm.c
index 6a77af6462a61d93a3c5c1bfb8fff214f546de62..36f7e36b6a573dc2738b4444d92da563ed5830c9 100644 (file)
--- a/libringbuffer/shm.c
+++ b/libringbuffer/shm.c
@@ -34,7 +34,7 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
 
        if (table->allocated_len >= table->size)
                return NULL;
-       obj = &table->objects[table->allocated_len++];
+       obj = &table->objects[table->allocated_len];
 
        /* wait_fd: create pipe */
        ret = pipe(waitfd);
@@ -55,7 +55,7 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
                PERROR("fcntl");
                goto error_fcntl;
        }
-       *obj->wait_fd = *waitfd;
+       memcpy(obj->wait_fd, waitfd, sizeof(waitfd));
 
        /* shm_fd: create shm */
 
@@ -67,8 +67,14 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
         * We specifically do _not_ use the / at the beginning of the
         * pathname so that some OS implementations can keep it local to
         * the process (POSIX leaves this implementation-defined).
+        * Ignore the shm_unlink errors, because we handle leaks that
+        * could occur by applications crashing between shm_open and
+        * shm_unlink by unlinking the shm before every open. Therefore,
+        * we can only leak one single shm (and only if the application
+        * crashes between shm_open and the following shm_unlink).
         */
        do {
+               (void) shm_unlink("ust-shm-tmp");
                shmfd = shm_open("ust-shm-tmp",
                                 O_CREAT | O_EXCL | O_RDWR, 0700);
        } while (shmfd < 0 && errno == EEXIST);
@@ -98,6 +104,8 @@ struct shm_object *shm_object_table_append(struct shm_object_table *table,
        obj->memory_map = memory_map;
        obj->memory_map_size = memory_map_size;
        obj->allocated_len = 0;
+       obj->index = table->allocated_len++;
+
        return obj;
 
 error_mmap:
@@ -118,7 +126,6 @@ error_fcntl:
                }
        }
 error_pipe:
-       free(obj);
        return NULL;
        
 }