patch "debugfs: fix security_locked_down() call for SELinux" added to driver-core-linus

This is a note to let you know that I've just added the patch titled

debugfs: fix security_locked_down() call for SELinux

to my driver-core git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
in the driver-core-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 5881fa8dc2de9697a89451f6518e8b3a796c09c6 Mon Sep 17 00:00:00 2001
From: Ondrej Mosnacek <[email protected]>
Date: Fri, 7 May 2021 14:53:04 +0200
Subject: debugfs: fix security_locked_down() call for SELinux

When (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) is zero, then the SELinux implementation of the locked_down hook might report a denial even though the operation would actually be allowed.

To fix this, make sure that security_locked_down() is called only when the return value will be taken into account (i.e. when changing one of the problematic attributes).

Note: this was introduced by commit 5496197f9b08 ("debugfs: Restrict debugfs when the kernel is locked down"), but it didn't matter at that time, as the SELinux support came in later.

---
 fs/debugfs/inode.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

index 1d252164d97b..8129a430d789 100644
@@ -45,10 +45,13 @@ static unsigned int debugfs_allow __ro_after_init = DEFAULT_DEBUGFS_ALLOW_BITS;
 static int debugfs_setattr(struct user_namespace *mnt_userns,
 			   struct dentry *dentry, struct iattr *ia)
 {
-	int ret = security_locked_down(LOCKDOWN_DEBUGFS);
+	int ret;
 
-	if (ret && (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
-		return ret;
+	if (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) {
+		ret = security_locked_down(LOCKDOWN_DEBUGFS);
+		if (ret)
+			return ret;
+	}
 	return simple_setattr(&init_user_ns, dentry, ia);
 }
 

2.31.1