btrfs: preserve i_mode if __btrfs_set_acl() fails

[ Upstream commit d7d824966530acfe32b94d1ed672e6fe1638cd68 ]

When changing a file's acl mask, btrfs_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 restoring the original mode bits if __btrfs_set_acl
fails.

Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>

diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 233bbc8789e07b637425fae82162926fde351a6a..6b16b8653d98ba71cbd1d06b5df9ff17c8766805 100644 (file)
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -118,13 +118,17 @@ out:
 int btrfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 {
        int ret;
+       umode_t old_mode = inode->i_mode;
 
        if (type == ACL_TYPE_ACCESS && acl) {
                ret = posix_acl_update_mode(inode, &inode->i_mode, &acl);
                if (ret)
                        return ret;
        }
-       return __btrfs_set_acl(NULL, inode, acl, type);
+       ret = __btrfs_set_acl(NULL, inode, acl, type);
+       if (ret)
+               inode->i_mode = old_mode;
+       return ret;
 }
 
 /*