[11/18] Btrfs: fix unprotected device list access when getting the fs information

Commit Message

Miao Xie Sept. 3, 2014, 1:35 p.m. UTC

When we get the fs information, we forgot to acquire the mutex of device list,
it might cause the problem we might access a device that was removed. Fix
it by acquiring the device list mutex.

Signed-off-by: Miao Xie <[e-mail]>
---
 fs/btrfs/super.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Patch

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 089991d..6b98358 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1703,7 +1703,11 @@  static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv;
 	int ret;
 
-	/* holding chunk_muext to avoid allocating new chunks */
+	/*
+	 * holding chunk_muext to avoid allocating new chunks, holding
+	 * device_list_mutex to avoid the device being removed
+	 */
+	mutex_lock(&fs_info->fs_devices->device_list_mutex);
 	mutex_lock(&fs_info->chunk_mutex);
 	rcu_read_lock();
 	list_for_each_entry_rcu(found, head, list) {
@@ -1744,11 +1748,13 @@  static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	ret = btrfs_calc_avail_data_space(fs_info->tree_root, &total_free_data);
 	if (ret) {
 		mutex_unlock(&fs_info->chunk_mutex);
+		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 		return ret;
 	}
 	buf->f_bavail += div_u64(total_free_data, factor);
 	buf->f_bavail = buf->f_bavail >> bits;
 	mutex_unlock(&fs_info->chunk_mutex);
+	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 
 	buf->f_type = BTRFS_SUPER_MAGIC;
 	buf->f_bsize = dentry->d_sb->s_blocksize;