From: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Date: Mon, 31 Jul 2017 02:43:41 +0000 (-0400)
Subject: ext4: preserve i_mode if __ext4_set_acl() fails
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=e4234d2c74ebfbac18198a14943d45b913649f78

ext4: preserve i_mode if __ext4_set_acl() fails

commit 397e434176bb62bc6068d2210af1d876c6212a7e upstream.

When changing a file's acl mask, __ext4_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.

Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index 5d419a496d96..b060bce2a67f 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -190,6 +190,8 @@ ext4_set_acl(handle_t *handle, struct inode *inode, int type,
 	void *value = NULL;
 	size_t size = 0;
 	int error;
+	int update_mode = 0;
+	umode_t mode = inode->i_mode;
 
 	if (S_ISLNK(inode->i_mode))
 		return -EOPNOTSUPP;
@@ -198,11 +200,10 @@ ext4_set_acl(handle_t *handle, struct inode *inode, int type,
 	case ACL_TYPE_ACCESS:
 		name_index = EXT4_XATTR_INDEX_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;
-			inode->i_ctime = ext4_current_time(inode);
-			ext4_mark_inode_dirty(handle, inode);
+			update_mode = 1;
 		}
 		break;
 
@@ -225,8 +226,14 @@ ext4_set_acl(handle_t *handle, struct inode *inode, int type,
 				      value, size, 0);
 
 	kfree(value);
-	if (!error)
+	if (!error) {
 		set_cached_acl(inode, type, acl);
+		if (update_mode) {
+			inode->i_mode = mode;
+			inode->i_ctime = ext4_current_time(inode);
+			ext4_mark_inode_dirty(handle, inode);
+		}
+	}
 
 	return error;
 }