seccomp: audit abnormal end to a process due to seccomp

The audit system likes to collect information about processes that end
abnormally (SIGSEGV) as this may me useful intrusion detection information.
This patch adds audit support to collect information when seccomp forces a
task to exit because of misbehavior in a similar way.

Signed-off-by: Eric Paris <[e-mail]>

include/linux/audit.h

···
 extern void __audit_inode(const char *name, const struct dentry *dentry);
 extern void __audit_inode_child(const struct dentry *dentry,
 				const struct inode *parent);
+extern void __audit_seccomp(unsigned long syscall);
 extern void __audit_ptrace(struct task_struct *t);
 
 static inline int audit_dummy_context(void)
···
 		__audit_inode_child(dentry, parent);
 }
 void audit_core_dumps(long signr);
+
+static inline void audit_seccomp(unsigned long syscall)
+{
+	if (unlikely(!audit_dummy_context()))
+		__audit_seccomp(syscall);
+}
 
 static inline void audit_ptrace(struct task_struct *t)
 {
···
 #define audit_inode(n,d) do { (void)(d); } while (0)
 #define audit_inode_child(i,p) do { ; } while (0)
 #define audit_core_dumps(i) do { ; } while (0)
+#define audit_seccomp(i) do { ; } while (0)
 #define auditsc_get_stamp(c,t,s) (0)
 #define audit_get_loginuid(t) (-1)
 #define audit_get_sessionid(t) (-1)

kernel/auditsc.c

···
 	context->type = AUDIT_MMAP;
 }
 
+static void audit_log_abend(struct audit_buffer *ab, char *reason, long signr)
+{
+	uid_t auid, uid;
+	gid_t gid;
+	unsigned int sessionid;
+
+	auid = audit_get_loginuid(current);
+	sessionid = audit_get_sessionid(current);
+	current_uid_gid(&uid, &gid);
+
+	audit_log_format(ab, "auid=%u uid=%u gid=%u ses=%u",
+			 auid, uid, gid, sessionid);
+	audit_log_task_context(ab);
+	audit_log_format(ab, " pid=%d comm=", current->pid);
+	audit_log_untrustedstring(ab, current->comm);
+	audit_log_format(ab, " reason=");
+	audit_log_string(ab, reason);
+	audit_log_format(ab, " sig=%ld", signr);
+}
 /**
  * audit_core_dumps - record information about processes that end abnormally
  * @signr: signal value
···
 void audit_core_dumps(long signr)
 {
 	struct audit_buffer *ab;
-	u32 sid;
-	uid_t auid = audit_get_loginuid(current), uid;
-	gid_t gid;
-	unsigned int sessionid = audit_get_sessionid(current);
 
 	if (!audit_enabled)
 		return;
···
 		return;
 
 	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_ANOM_ABEND);
-	current_uid_gid(&uid, &gid);
-	audit_log_format(ab, "auid=%u uid=%u gid=%u ses=%u",
-			 auid, uid, gid, sessionid);
-	security_task_getsecid(current, &sid);
-	if (sid) {
-		char *ctx = NULL;
-		u32 len;
+	audit_log_abend(ab, "memory violation", signr);
+	audit_log_end(ab);
+}
 
-		if (security_secid_to_secctx(sid, &ctx, &len))
-			audit_log_format(ab, " ssid=%u", sid);
-		else {
-			audit_log_format(ab, " subj=%s", ctx);
-			security_release_secctx(ctx, len);
-		}
-	}
-	audit_log_format(ab, " pid=%d comm=", current->pid);
-	audit_log_untrustedstring(ab, current->comm);
-	audit_log_format(ab, " sig=%ld", signr);
+void __audit_seccomp(unsigned long syscall)
+{
+	struct audit_buffer *ab;
+
+	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_ANOM_ABEND);
+	audit_log_abend(ab, "seccomp", SIGKILL);
+	audit_log_format(ab, " syscall=%ld", syscall);
 	audit_log_end(ab);
 }
 

kernel/seccomp.c

···
  * This defines a simple but solid secure-computing mode.
  */
 
+#include <linux/audit.h>
 #include <linux/seccomp.h>
 #include <linux/sched.h>
 #include <linux/compat.h>
···
 #ifdef SECCOMP_DEBUG
 	dump_stack();
 #endif
+	audit_seccomp(this_syscall);
 	do_exit(SIGKILL);
 }