ext4: preserve i_mode if __ext4_set_acl() fails

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>

diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index 09441ae07a5be9de1f18cdc01d896808ba1e02be..2985cd0a640d9ecd65208e96383bc9ad5d7305c1 100644 (file)
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -189,16 +189,17 @@ __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;
 
        switch (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 = current_time(inode);
-                       ext4_mark_inode_dirty(handle, inode);
+                       update_mode = 1;
                }
                break;
 
@@ -221,8 +222,14 @@ __ext4_set_acl(handle_t *handle, struct inode *inode, int type,
                                      value, size, xattr_flags);
 
        kfree(value);
-       if (!error)
+       if (!error) {
                set_cached_acl(inode, type, acl);
+               if (update_mode) {
+                       inode->i_mode = mode;
+                       inode->i_ctime = current_time(inode);
+                       ext4_mark_inode_dirty(handle, inode);
+               }
+       }
 
        return error;
 }