Commit 5881fa8d authored by Ondrej Mosnacek's avatar Ondrej Mosnacek Committed by Greg Kroah-Hartman
Browse files

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 5496197f ("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: 59438b46 ("security,lockdown,selinux: implement SELinux lockdown")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarOndrej Mosnacek <omosnace@redhat.com>
Link: https://lore.kernel.org/r/20210507125304.144394-1-omosnace@redhat.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d07f6ca9

fs/debugfs/inode.c

+6 −3
Original line number Diff line number Diff line
@@ -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)))

	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);

}