linux-ext4 - [PATCH 5/5] reiserfs: preserve i_mode if __reiserfs_set

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Message-ID: <3ab632985cbf6fdd2ee5284482b9749c5893a5a1.1499805488.git.ernesto.mnd.fernandez@gmail.com>
Date:   Wed, 12 Jul 2017 06:56:04 -0300
From:   Ernesto A. Fernández 
        <ernesto.mnd.fernandez@...il.com>
To:     Jan Kara <jack@...e.com>, Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Dave Kleikamp <shaggy@...nel.org>, linux-ext4@...r.kernel.org,
        jfs-discussion@...ts.sourceforge.net,
        reiserfs-devel@...r.kernel.org
Subject: [PATCH 5/5] reiserfs: preserve i_mode if __reiserfs_set_acl() fails

When changing a file's acl mask, __reiserfs_set_acl() will first set the
group bits of i_mode to the value of the mask, and only then set the
actual extended attribute representing the new acl.

If the second part fails (due to lack of space, for example) and the file
had no acl attribute to begin with, the system will from now on assume
that the mask permission bits are actual group permission bits, potentially
granting access to the wrong users.

Prevent this by only changing the inode mode after the acl has been set.
Also make reiserfs_xattr_set_handle() return -ENODATA only in case of
actual error, and return 0 when requested deletion of a nonexistent acl.
This is more consistent with the behaviour of other *_xattr_set()
functions and makes the patch simpler.

Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@...il.com>
---
 fs/reiserfs/xattr.c     |  4 ++++
 fs/reiserfs/xattr_acl.c | 25 +++++++++----------------
 2 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c
index e87aa21..936a57a 100644
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -513,6 +513,10 @@ reiserfs_xattr_set_handle(struct reiserfs_transaction_handle *th,
 
 	if (!buffer) {
 		err = lookup_and_delete_xattr(inode, name);
+		if (flags & XATTR_REPLACE)
+			return err;
+		if (err == -ENODATA)
+			err = 0;
 		return err;
 	}
 
diff --git a/fs/reiserfs/xattr_acl.c b/fs/reiserfs/xattr_acl.c
index 3d2256a..c02e5ac 100644
--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -237,14 +237,17 @@ __reiserfs_set_acl(struct reiserfs_transaction_handle *th, struct inode *inode,
 	void *value = NULL;
 	size_t size = 0;
 	int error;
+	int update_mode = 0;
+	umode_t mode = inode->i_mode;
 
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name = XATTR_NAME_POSIX_ACL_ACCESS;
 		if (acl) {
-			error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+			error = posix_acl_update_mode(inode, &mode, &acl);
 			if (error)
 				return error;
+			update_mode = 1;
 		}
 		break;
 	case ACL_TYPE_DEFAULT:
@@ -264,25 +267,15 @@ __reiserfs_set_acl(struct reiserfs_transaction_handle *th, struct inode *inode,
 
 	error = reiserfs_xattr_set_handle(th, inode, name, value, size, 0);
 
-	/*
-	 * Ensure that the inode gets dirtied if we're only using
-	 * the mode bits and an old ACL didn't exist. We don't need
-	 * to check if the inode is hashed here since we won't get
-	 * called by reiserfs_inherit_default_acl().
-	 */
-	if (error == -ENODATA) {
-		error = 0;
-		if (type == ACL_TYPE_ACCESS) {
+	kfree(value);
+	if (!error) {
+		set_cached_acl(inode, type, acl);
+		if (update_mode) {
+			inode->i_mode = mode;
 			inode->i_ctime = current_time(inode);
 			mark_inode_dirty(inode);
 		}
 	}
-
-	kfree(value);
-
-	if (!error)
-		set_cached_acl(inode, type, acl);
-
 	return error;
 }
 
-- 
2.1.4