[PATCH 3.16 057/129] ext4: fix check of inode in swap_inode_boot_loader

[Ben Hutchings]

3.16.70-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: yangerkun <yangerkun@xxxxxxxxxx>

commit 67a11611e1a5211f6569044fbf8150875764d1d0 upstream.

Before really do swap between inode and boot inode, something need to
check to avoid invalid or not permitted operation, like does this inode
has inline data. But the condition check should be protected by inode
lock to avoid change while swapping. Also some other condition will not
change between swapping, but there has no problem to do this under inode
lock.

Signed-off-by: yangerkun <yangerkun@xxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
[bwh: Backported to 3.16: There's no support or test for filesytem encryption]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/ext4/ioctl.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -118,15 +118,6 @@ static long swap_inode_boot_loader(struc
 	struct ext4_inode_info *ei_bl;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 
-	if (inode->i_nlink != 1 || !S_ISREG(inode->i_mode) ||
-	    IS_SWAPFILE(inode) ||
-	    ext4_has_inline_data(inode))
-		return -EINVAL;
-
-	if (IS_RDONLY(inode) || IS_APPEND(inode) || IS_IMMUTABLE(inode) ||
-	    !inode_owner_or_capable(inode) || !capable(CAP_SYS_ADMIN))
-		return -EPERM;
-
 	inode_bl = ext4_iget(sb, EXT4_BOOT_LOADER_INO, EXT4_IGET_SPECIAL);
 	if (IS_ERR(inode_bl))
 		return PTR_ERR(inode_bl);
@@ -139,6 +130,19 @@ static long swap_inode_boot_loader(struc
 	 * that only 1 swap_inode_boot_loader is running. */
 	lock_two_nondirectories(inode, inode_bl);
 
+	if (inode->i_nlink != 1 || !S_ISREG(inode->i_mode) ||
+	    IS_SWAPFILE(inode) ||
+	    ext4_has_inline_data(inode)) {
+		err = -EINVAL;
+		goto journal_err_out;
+	}
+
+	if (IS_RDONLY(inode) || IS_APPEND(inode) || IS_IMMUTABLE(inode) ||
+	    !inode_owner_or_capable(inode) || !capable(CAP_SYS_ADMIN)) {
+		err = -EPERM;
+		goto journal_err_out;
+	}
+
 	/* Wait for all existing dio workers */
 	ext4_inode_block_unlocked_dio(inode);
 	ext4_inode_block_unlocked_dio(inode_bl);