[PATCH 4.14 33/38] apparmor: fix regression in mount mediation when feature set is pinned

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: John Johansen <john.johansen@canonical.com>

commit 5b9f57cf47b87f07210875d6a24776b4496b818d upstream.

When the mount code was refactored for Labels it was not correctly
updated to check whether policy supported mediation of the mount
class.  This causes a regression when the kernel feature set is
reported as supporting mount and policy is pinned to a feature set
that does not support mount mediation.

BugLink: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=882697#41
Fixes: 2ea3ffb7782a ("apparmor: add mount mediation")
Reported-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 security/apparmor/mount.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/security/apparmor/mount.c
+++ b/security/apparmor/mount.c
@@ -330,6 +330,9 @@ static int match_mnt_path_str(struct aa_
 	AA_BUG(!mntpath);
 	AA_BUG(!buffer);
 
+	if (!PROFILE_MEDIATES(profile, AA_CLASS_MOUNT))
+		return 0;
+
 	error = aa_path_name(mntpath, path_flags(profile, mntpath), buffer,
 			     &mntpnt, &info, profile->disconnected);
 	if (error)
@@ -381,6 +384,9 @@ static int match_mnt(struct aa_profile *
 	AA_BUG(!profile);
 	AA_BUG(devpath && !devbuffer);
 
+	if (!PROFILE_MEDIATES(profile, AA_CLASS_MOUNT))
+		return 0;
+
 	if (devpath) {
 		error = aa_path_name(devpath, path_flags(profile, devpath),
 				     devbuffer, &devname, &info,
@@ -559,6 +565,9 @@ static int profile_umount(struct aa_prof
 	AA_BUG(!profile);
 	AA_BUG(!path);
 
+	if (!PROFILE_MEDIATES(profile, AA_CLASS_MOUNT))
+		return 0;
+
 	error = aa_path_name(path, path_flags(profile, path), buffer, &name,
 			     &info, profile->disconnected);
 	if (error)
@@ -614,7 +623,8 @@ static struct aa_label *build_pivotroot(
 	AA_BUG(!new_path);
 	AA_BUG(!old_path);
 
-	if (profile_unconfined(profile))
+	if (profile_unconfined(profile) ||
+	    !PROFILE_MEDIATES(profile, AA_CLASS_MOUNT))
 		return aa_get_newest_label(&profile->label);
 
 	error = aa_path_name(old_path, path_flags(profile, old_path),