[PATCH] protect ext3 ioctl modifying append_only, immutable, etc. with i_mutex

All modifications of ->i_flags in inodes that might be visible to
somebody else must be under ->i_mutex.  That patch fixes ext3 ioctl()
setting S_APPEND and friends.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/ext3/ioctl.c

@@ -48,6 +48,7 @@ int ext3_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
 		if (!S_ISDIR(inode->i_mode))
 			flags &= ~EXT3_DIRSYNC_FL;
 
+		mutex_lock(&inode->i_mutex);
 		oldflags = ei->i_flags;
 
 		/* The JOURNAL_DATA flag is modifiable only by root */
@@ -60,23 +61,29 @@ int ext3_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
 		 * This test looks nicer. Thanks to Pauline Middelink
 		 */
 		if ((flags ^ oldflags) & (EXT3_APPEND_FL | EXT3_IMMUTABLE_FL)) {
-			if (!capable(CAP_LINUX_IMMUTABLE))
+			if (!capable(CAP_LINUX_IMMUTABLE)) {
+				mutex_unlock(&inode->i_mutex);
 				return -EPERM;
 			}
+		}
 
 		/*
 		 * The JOURNAL_DATA flag can only be changed by
 		 * the relevant capability.
 		 */
 		if ((jflag ^ oldflags) & (EXT3_JOURNAL_DATA_FL)) {
-			if (!capable(CAP_SYS_RESOURCE))
+			if (!capable(CAP_SYS_RESOURCE)) {
+				mutex_unlock(&inode->i_mutex);
 				return -EPERM;
 			}
+		}
 
 
 		handle = ext3_journal_start(inode, 1);
-		if (IS_ERR(handle))
+		if (IS_ERR(handle)) {
+			mutex_unlock(&inode->i_mutex);
 			return PTR_ERR(handle);
+		}
 		if (IS_SYNC(inode))
 			handle->h_sync = 1;
 		err = ext3_reserve_inode_write(handle, inode, &iloc);
@@ -93,11 +100,14 @@ int ext3_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
 		err = ext3_mark_iloc_dirty(handle, inode, &iloc);
 flags_err:
 		ext3_journal_stop(handle);
-		if (err)
+		if (err) {
+			mutex_unlock(&inode->i_mutex);
 			return err;
+		}
 
 		if ((jflag ^ oldflags) & (EXT3_JOURNAL_DATA_FL))
 			err = ext3_change_inode_journal_flag(inode, jflag);
+		mutex_unlock(&inode->i_mutex);
 		return err;
 	}
 	case EXT3_IOC_GETVERSION: