UBUNTU: SAUCE: apparmor4.0.0 [69/90]: add io_uring mediation

BugLink: http://bugs.launchpad.net/bugs/2028253

For now, the io_uring mediation is limited to sqpoll and
override_creds.

Signed-off-by: Georgia Garcia <georgia.garcia@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
(cherry picked from https://gitlab.com/jjohansen/apparmor-kernel)
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
(cherry picked from commit d4bbbd67b37fb77205cef0c175dd6f88cf37fdaa
https://git.launchpad.net/~apparmor-dev/ubuntu-kernel-next)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

security/apparmor/apparmorfs.c

@@ -2584,6 +2584,8 @@ static struct aa_sfs_entry aa_sfs_entry_domain[] = {
 static struct aa_sfs_entry aa_sfs_entry_unconfined[] = {
 	AA_SFS_FILE_BOOLEAN("change_profile", 1),
 	AA_SFS_FILE_INTPTR("userns",		aa_unprivileged_userns_restricted),
+	AA_SFS_FILE_INTPTR("io_uring",
+			    aa_unprivileged_uring_restricted),
 	{ }
 };
 

security/apparmor/include/policy.h

@@ -38,6 +38,7 @@ extern int aa_unprivileged_userns_restricted;
 extern int aa_unprivileged_userns_restricted_force;
 extern int aa_unprivileged_userns_restricted_complain;
 extern int aa_unprivileged_unconfined_restricted;
+extern int aa_unprivileged_uring_restricted;
 
 extern const char *const aa_profile_mode_names[];
 #define APPARMOR_MODE_NAMES_MAX_INDEX 4

security/apparmor/lsm.c

@@ -803,13 +803,41 @@ static int profile_uring(struct aa_profile *profile, u32 request,
 {
 	unsigned int state;
 	struct aa_ruleset *rules;
-	int error = 0;
 
 	AA_BUG(!profile);
 
 	rules = list_first_entry(&profile->rules, typeof(*rules), list);
+
+	/* TODO: rework unconfined profile/dfa to mediate user ns, then
+	 * we can drop the unconfined test
+	 */
 	state = RULE_MEDIATES(rules, AA_CLASS_IO_URING);
-	if (state) {
+	if (!state) {
+		/* TODO: this gets replaced when the default unconfined
+		 * profile dfa gets updated to handle this
+		 */
+		if (profile_unconfined(profile) &&
+		    profile == profiles_ns(profile)->unconfined) {
+			if (!aa_unprivileged_uring_restricted ||
+			    ns_capable_noaudit(current_user_ns(), cap))
+				/* unconfined early bail out */
+				return 0;
+			/* unconfined unprivileged user */
+			/* don't just return: allow complain mode to override */
+		} else {
+			/* Fallback to capability check if profile doesn't
+			 * support io_uring rules. Note: special unconfined
+			 * profiles as well.
+			 */
+			return aa_capable(current_cred(), &profile->label,
+					  cap, CAP_OPT_NONE);
+		}
+		/* continue to mediation - !state means non-accepting
+		 * but can be overidden by complain
+		 */
+	}
+	/* block so perms is not initialized unless mediating */
+	do {
 		struct aa_perms perms = { };
 
 		if (new) {
@@ -819,11 +847,11 @@ static int profile_uring(struct aa_profile *profile, u32 request,
 			perms = *aa_lookup_perms(rules->policy, state);
 		}
 		aa_apply_modes_to_perms(profile, &perms);
-		error = aa_check_perms(profile, &perms, request, ad,
+		return aa_check_perms(profile, &perms, request, ad,
 				       audit_uring_cb);
-	}
+	} while (0);
 
-	return error;
+	return 0;
 }
 
 /**
@@ -2406,6 +2434,13 @@ static struct ctl_table apparmor_sysctl_table[] = {
 		.mode           = 0600,
 		.proc_handler   = apparmor_dointvec,
 	},
+	{
+		.procname       = "apparmor_restrict_unprivileged_io_uring",
+		.data           = &aa_unprivileged_uring_restricted,
+		.maxlen         = sizeof(int),
+		.mode           = 0600,
+		.proc_handler   = apparmor_dointvec,
+	},
 	{ }
 };
 

security/apparmor/policy.c

@@ -92,6 +92,7 @@ int aa_unprivileged_userns_restricted = IS_ENABLED(CONFIG_SECURITY_APPARMOR_REST
 int aa_unprivileged_userns_restricted_force;
 int aa_unprivileged_userns_restricted_complain;
 int aa_unprivileged_unconfined_restricted;
+int aa_unprivileged_uring_restricted;
 
 const char *const aa_profile_mode_names[] = {
 	"enforce",