[PATCH] debugfs: fix security_locked_down() call for SELinux

* [PATCH] debugfs: fix security_locked_down() call for SELinux
@ 2021-05-07 11:41 Ondrej Mosnacek
  2021-05-07 12:03 ` Greg Kroah-Hartman
  0 siblings, 1 reply; 5+ messages in thread
From: Ondrej Mosnacek @ 2021-05-07 11:41 UTC (permalink / raw)
  To: Greg Kroah-Hartman
  Cc: Rafael J. Wysocki, selinux, linux-security-module, James Morris,
	linux-fsdevel, linux-kernel

Make sure that security_locked_down() is checked last so that a bogus
denial is not reported by SELinux when (ia->ia_valid & (ATTR_MODE |
ATTR_UID | ATTR_GID)) is zero.

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.

Fixes: 59438b46471a ("security,lockdown,selinux: implement SELinux lockdown")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
---
 fs/debugfs/inode.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 22e86ae4dd5a..bbfc7898c1aa 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -45,10 +45,13 @@ static unsigned int debugfs_allow = 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


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