From:   Michal Suchanek <msuchanek@suse.de>
To:     linux-kernel@vger.kernel.org
Cc:     Michal Suchanek <msuchanek@suse.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Matthew Garrett <matthewgarrett@google.com>,
        James Morris <jmorris@namei.org>,
        David Howells <dhowells@redhat.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        acpi4asus-user@lists.sourceforge.net,
        platform-driver-x86@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>, Greg KH <greg@kroah.com>
Subject: [PATCH] debugfs: lockdown: Allow reading debugfs files that are not world readable
Date:   Tue,  4 Jan 2022 18:05:05 +0100
Message-Id: <20220104170505.10248-1-msuchanek@suse.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk


When the kernel is locked down the kernel allows reading only debugfs
files with mode 444. Mode 400 is also valid but is not allowed.

Make the 444 into a mask.

Fixes: 5496197f9b08 ("debugfs: Restrict debugfs when the kernel is locked down")
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
 fs/debugfs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 7d162b0efbf0..950c63fa4d0b 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -147,7 +147,7 @@ static int debugfs_locked_down(struct inode *inode,
 			       struct file *filp,
 			       const struct file_operations *real_fops)
 {
-	if ((inode->i_mode & 07777) == 0444 &&
+	if ((inode->i_mode & 07777 & ~0444) == 0 &&
 	    !(filp->f_mode & FMODE_WRITE) &&
 	    !real_fops->unlocked_ioctl &&
 	    !real_fops->compat_ioctl &&
-- 
2.31.1