apparmor: add io_uring mediation

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>

security/apparmor/apparmorfs.c

@@ -2390,6 +2390,12 @@ static struct aa_sfs_entry aa_sfs_entry_query[] = {
 	AA_SFS_DIR("label",			aa_sfs_entry_query_label),
 	{ }
 };
+
+static struct aa_sfs_entry aa_sfs_entry_io_uring[] = {
+	AA_SFS_FILE_STRING("mask", "sqpoll override_creds"),
+	{ }
+};
+
 static struct aa_sfs_entry aa_sfs_entry_features[] = {
 	AA_SFS_DIR("policy",			aa_sfs_entry_policy),
 	AA_SFS_DIR("domain",			aa_sfs_entry_domain),
@@ -2403,6 +2409,7 @@ static struct aa_sfs_entry aa_sfs_entry_features[] = {
 	AA_SFS_DIR("ptrace",			aa_sfs_entry_ptrace),
 	AA_SFS_DIR("signal",			aa_sfs_entry_signal),
 	AA_SFS_DIR("query",			aa_sfs_entry_query),
+	AA_SFS_DIR("io_uring",			aa_sfs_entry_io_uring),
 	{ }
 };
 

security/apparmor/audit.c

@@ -59,7 +59,7 @@ static const char *const aa_class_names[] = {
 	"module",
 	"lsm",
 	"namespace",
-	"unknown",
+	"io_uring",
 	"unknown",
 	"unknown",
 	"unknown",

security/apparmor/include/apparmor.h

@@ -30,10 +30,10 @@
 #define AA_CLASS_NET		14
 #define AA_CLASS_LABEL		16
 #define AA_CLASS_POSIX_MQUEUE	17
-#define AA_CLASS_IO_URING	18
 #define AA_CLASS_MODULE		19
 #define AA_CLASS_DISPLAY_LSM	20
 #define AA_CLASS_NS		21
+#define AA_CLASS_IO_URING	22
 
 #define AA_CLASS_X		31
 #define AA_CLASS_DBUS		32

security/apparmor/include/audit.h

@@ -105,6 +105,9 @@ enum audit_type {
 
 #define OP_USERNS_CREATE "userns_create"
 
+#define OP_URING_OVERRIDE "uring_override"
+#define OP_URING_SQPOLL "uring_sqpoll"
+
 struct apparmor_audit_data {
 	int error;
 	int type;
@@ -153,6 +156,9 @@ struct apparmor_audit_data {
 			const char *data;
 			unsigned long flags;
 		} mnt;
+		struct {
+			struct aa_label *target;
+		} uring;
 	};
 
 	struct common_audit_data common;

security/apparmor/include/perms.h

@@ -48,6 +48,9 @@
 
 #define AA_LINK_SUBSET		AA_MAY_LOCK	/* overlaid */
 
+#define AA_MAY_CREATE_SQPOLL   AA_MAY_CREATE
+#define AA_MAY_OVERRIDE_CRED   AA_MAY_APPEND
+#define AA_URING_PERM_MASK     (AA_MAY_OVERRIDE_CRED | AA_MAY_CREATE_SQPOLL)
 
 #define PERMS_CHRS_MASK (MAY_READ | MAY_WRITE | AA_MAY_CREATE |		\
 			 AA_MAY_DELETE | AA_MAY_LINK | AA_MAY_LOCK |	\

security/apparmor/lsm.c

@@ -582,6 +582,114 @@ static int apparmor_file_mprotect(struct vm_area_struct *vma,
 			   false);
 }
 
+#ifdef CONFIG_IO_URING
+static const char *audit_uring_mask(u32 mask)
+{
+	if (mask & AA_MAY_CREATE_SQPOLL)
+		return "sqpoll";
+	if (mask & AA_MAY_OVERRIDE_CRED)
+		return "override_creds";
+	return "";
+}
+
+static void audit_uring_cb(struct audit_buffer *ab, void *va)
+{
+	struct apparmor_audit_data *ad = aad_of_va(va);
+
+	if (ad->request & AA_URING_PERM_MASK) {
+		audit_log_format(ab, " requested=\"%s\"",
+				 audit_uring_mask(ad->request));
+		if (ad->denied & AA_URING_PERM_MASK) {
+			audit_log_format(ab, " denied=\"%s\"",
+					 audit_uring_mask(ad->denied));
+		}
+	}
+	if (ad->uring.target) {
+		audit_log_format(ab, " tcontext=");
+		aa_label_xaudit(ab, labels_ns(ad->subj_label),
+				ad->uring.target,
+				FLAGS_NONE, GFP_ATOMIC);
+	}
+}
+
+static int profile_uring(struct aa_profile *profile, u32 request,
+			 struct aa_label *new, int cap,
+			 struct apparmor_audit_data *ad)
+{
+	unsigned int state;
+	struct aa_ruleset *rules;
+	int error = 0;
+
+	AA_BUG(!profile);
+
+	rules = list_first_entry(&profile->rules, typeof(*rules), list);
+	state = RULE_MEDIATES(rules, AA_CLASS_IO_URING);
+	if (state) {
+		struct aa_perms perms = { };
+
+		if (new) {
+			aa_label_match(profile, rules, new, state,
+				       false, request, &perms);
+		} else {
+			perms = *aa_lookup_perms(rules->policy, state);
+		}
+		aa_apply_modes_to_perms(profile, &perms);
+		error = aa_check_perms(profile, &perms, request, ad,
+				       audit_uring_cb);
+	}
+
+	return error;
+}
+
+/**
+ * apparmor_uring_override_creds - check the requested cred override
+ * @new: the target creds
+ *
+ * Check to see if the current task is allowed to override it's credentials
+ * to service an io_uring operation.
+ */
+int apparmor_uring_override_creds(const struct cred *new)
+{
+	struct aa_profile *profile;
+	struct aa_label *label;
+	int error;
+	DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_NONE, AA_CLASS_IO_URING,
+			  OP_URING_OVERRIDE);
+
+	ad.uring.target = cred_label(new);
+	label = __begin_current_label_crit_section();
+	error = fn_for_each(label, profile,
+			profile_uring(profile, AA_MAY_OVERRIDE_CRED,
+				      cred_label(new), CAP_SYS_ADMIN, &ad));
+	__end_current_label_crit_section(label);
+
+	return error;
+}
+
+/**
+ * apparmor_uring_sqpoll - check if a io_uring polling thread can be created
+ *
+ * Check to see if the current task is allowed to create a new io_uring
+ * kernel polling thread.
+ */
+int apparmor_uring_sqpoll(void)
+{
+	struct aa_profile *profile;
+	struct aa_label *label;
+	int error;
+	DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_NONE, AA_CLASS_IO_URING,
+			  OP_URING_SQPOLL);
+
+	label = __begin_current_label_crit_section();
+	error = fn_for_each(label, profile,
+			profile_uring(profile, AA_MAY_CREATE_SQPOLL,
+				      NULL, CAP_SYS_ADMIN, &ad));
+	__end_current_label_crit_section(label);
+
+	return error;
+}
+#endif /* CONFIG_IO_URING */
+
 static int apparmor_sb_mount(const char *dev_name, const struct path *path,
 			     const char *type, unsigned long flags, void *data)
 {
@@ -1346,6 +1454,11 @@ static struct security_hook_list apparmor_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(secid_to_secctx, apparmor_secid_to_secctx),
 	LSM_HOOK_INIT(secctx_to_secid, apparmor_secctx_to_secid),
 	LSM_HOOK_INIT(release_secctx, apparmor_release_secctx),
+
+#ifdef CONFIG_IO_URING
+	LSM_HOOK_INIT(uring_override_creds, apparmor_uring_override_creds),
+	LSM_HOOK_INIT(uring_sqpoll, apparmor_uring_sqpoll),
+#endif
 };
 
 /*