ext{3,4}: Fix potential race when setversion ioctl updates inode

The EXT{3,4}_IOC_SETVERSION ioctl() updates i_ctime and i_generation
without i_mutex. This can lead to a race with the other operations that
update i_ctime. This is not a big issue but let's make the ioctl consistent
with how we handle e.g. other timestamp updates and use i_mutex to protect
inode changes.

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext3/ioctl.c

@@ -134,10 +134,11 @@ flags_out:
 			goto setversion_out;
 		}
 
+		mutex_lock(&inode->i_mutex);
 		handle = ext3_journal_start(inode, 1);
 		if (IS_ERR(handle)) {
 			err = PTR_ERR(handle);
-			goto setversion_out;
+			goto unlock_out;
 		}
 		err = ext3_reserve_inode_write(handle, inode, &iloc);
 		if (err == 0) {
@@ -146,6 +147,9 @@ flags_out:
 			err = ext3_mark_iloc_dirty(handle, inode, &iloc);
 		}
 		ext3_journal_stop(handle);
+
+unlock_out:
+		mutex_unlock(&inode->i_mutex);
 setversion_out:
 		mnt_drop_write(filp->f_path.mnt);
 		return err;

fs/ext4/ioctl.c

@@ -158,10 +158,11 @@ flags_out:
 			goto setversion_out;
 		}
 
+		mutex_lock(&inode->i_mutex);
 		handle = ext4_journal_start(inode, 1);
 		if (IS_ERR(handle)) {
 			err = PTR_ERR(handle);
-			goto setversion_out;
+			goto unlock_out;
 		}
 		err = ext4_reserve_inode_write(handle, inode, &iloc);
 		if (err == 0) {
@@ -170,6 +171,9 @@ flags_out:
 			err = ext4_mark_iloc_dirty(handle, inode, &iloc);
 		}
 		ext4_journal_stop(handle);
+
+unlock_out:
+		mutex_unlock(&inode->i_mutex);
 setversion_out:
 		mnt_drop_write(filp->f_path.mnt);
 		return err;