debugfs: lockdown: Allow reading debugfs files that are not world readable

[ Upstream commit 358fcf5ddbec4e6706405847d6a666f5933a6c25 ]

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>
Link: https://lore.kernel.org/r/20220104170505.10248-1-msuchanek@suse.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 3aa5eb9ce498e46b89ef40e7cc900378de3bb29a..96059af28f5084827dceda7aaac2bb8094fe36cc 100644 (file)
--- 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 &&