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https://gitlab.freedesktop.org/pipewire/pipewire
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pipewire-v4l2: only access globals.file_maps
while holding globals.lock
`file_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 `file_map` pointers may be invalidated. Hence it is only safe to access `file_map` structs while holding `globals.lock`, which prevents any modifications to the file map array, thus keeping the references valid.
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@ -362,24 +362,34 @@ static int add_file_map(void *addr, 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 file_map *find_file_map(void *addr)
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/* must be called with `globals.lock` held */
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static struct file_map *find_file_map_unlocked(void *addr)
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{
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struct file_map *map, *res = NULL;
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pthread_mutex_lock(&globals.lock);
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struct file_map *map;
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pw_array_for_each(map, &globals.file_maps) {
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if (map->addr == addr) {
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res = map;
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break;
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}
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if (map->addr == addr)
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return map;
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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 void remove_file_map(struct file_map *map)
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static struct file *remove_file_map(void *addr)
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{
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pthread_mutex_lock(&globals.lock);
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pw_array_remove(&globals.file_maps, map);
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struct file_map *map = find_file_map_unlocked(addr);
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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.file_maps, map);
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}
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pthread_mutex_unlock(&globals.lock);
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return file;
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}
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static int add_buffer_map(struct file *file, void *addr, uint32_t id)
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@ -729,9 +739,9 @@ static int v4l2_dup(int oldfd)
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static int v4l2_close(int fd)
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{
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struct file *file = remove_fd_map(fd);
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struct file *file;
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if (file == NULL)
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if ((file = remove_fd_map(fd)) == NULL)
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return globals.old_fops.close(fd);
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unref_file(file);
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@ -1852,15 +1862,12 @@ error_unlock:
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static int v4l2_munmap(void *addr, size_t length)
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{
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int res;
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struct file_map *fmap;
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struct buffer_map *bmap;
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struct file *file;
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if ((fmap = find_file_map(addr)) == NULL)
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if ((file = remove_file_map(addr)) == NULL)
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return globals.old_fops.munmap(addr, length);
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file = fmap->file;
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pw_thread_loop_lock(file->loop);
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bmap = find_buffer_map(file, addr);
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@ -1879,8 +1886,6 @@ static int v4l2_munmap(void *addr, size_t length)
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exit_unlock:
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pw_thread_loop_unlock(file->loop);
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remove_file_map(fmap);
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return res;
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}
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