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https://gitlab.freedesktop.org/pipewire/pipewire
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pipewire-v4l2: only access globals.fd_maps
while holding globals.lock
`fd_map` structures are allocated in a `pw_array`. When inserting into a full `pw_array`, it is resized to accomodate the new elements. In that case, all `fd_map` pointers may be invalidated. Hence it is only safe to access `fd_map` structs while holding `globals.lock`, which prevents any modifications to the fd map array, thus keeping the references valid.
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@ -299,37 +299,55 @@ static int add_fd_map(int fd, struct file *file)
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pthread_mutex_unlock(&globals.lock);
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return 0;
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}
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static struct fd_map *find_fd_map(int fd)
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/* must be called with `globals.lock` held */
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static struct fd_map *find_fd_map_unlocked(int fd)
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{
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struct fd_map *map, *res = NULL;
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pthread_mutex_lock(&globals.lock);
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struct fd_map *map;
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pw_array_for_each(map, &globals.fd_maps) {
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if (map->fd == fd) {
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ATOMIC_INC(map->file->ref);
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res = map;
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break;
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return map;
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}
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}
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pthread_mutex_unlock(&globals.lock);
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return res;
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return NULL;
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}
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static struct file *find_file(int fd)
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{
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struct fd_map *map = find_fd_map(fd);
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if (map == NULL)
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return NULL;
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return map->file;
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}
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static void remove_fd_map(struct fd_map *map)
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{
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struct file *file = map->file;
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pthread_mutex_lock(&globals.lock);
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pw_array_remove(&globals.fd_maps, map);
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struct fd_map *map = find_fd_map_unlocked(fd);
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struct file *file = NULL;
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if (map != NULL)
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file = map->file;
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pthread_mutex_unlock(&globals.lock);
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unref_file(file);
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return file;
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}
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static struct file *remove_fd_map(int fd)
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{
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pthread_mutex_lock(&globals.lock);
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struct fd_map *map = find_fd_map_unlocked(fd);
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struct file *file = NULL;
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if (map != NULL) {
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file = map->file;
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pw_array_remove(&globals.fd_maps, map);
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}
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pthread_mutex_unlock(&globals.lock);
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if (file != NULL)
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unref_file(file);
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return file;
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}
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static int add_file_map(void *addr, struct file *file)
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@ -711,20 +729,15 @@ static int v4l2_dup(int oldfd)
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static int v4l2_close(int fd)
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{
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int res = 0;
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struct file *file;
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struct fd_map *map;
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struct file *file = remove_fd_map(fd);
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if ((map = find_fd_map(fd)) == NULL)
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if (file == NULL)
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return globals.old_fops.close(fd);
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file = map->file;
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remove_fd_map(map);
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unref_file(file);
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pw_log_info("fd:%d -> %d (%s)", fd,
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res, strerror(res < 0 ? errno : 0));
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return res;
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pw_log_info("fd:%d closed", fd);
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return 0;
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}
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#define KERNEL_VERSION(a, b, c) (((a) << 16) + ((b) << 8) + (c))
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