[PATCH 2/2] seccomp: Audit SECCOMP_RET_ERRNO actions with errno values

[Tyler Hicks <tyhicks@canonical.com>]

Generate audit records for SECCOMP_RET_ERRNO actions, which were
previously not audited.

Additionally, include the errno value that will be set in the audit
message.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
---
 include/linux/audit.h | 19 ++++++++++++++++++-
 kernel/auditsc.c      |  3 +++
 kernel/seccomp.c      |  4 +++-
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 8c588c3..6815812 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -87,7 +87,10 @@ struct audit_field {
 
 struct audit_seccomp_info {
 	int		code;
-	long		signr;
+	union {
+		int	errno;
+		long	signr;
+	};
 };
 
 extern int is_audit_feature_set(int which);
@@ -319,6 +322,20 @@ static inline void audit_inode_child(struct inode *parent,
 }
 void audit_core_dumps(long signr);
 
+static inline void audit_seccomp_errno(unsigned long syscall, int errno,
+				       int code)
+{
+	if (!audit_enabled)
+		return;
+
+	if (errno || unlikely(!audit_dummy_context())) {
+		struct audit_seccomp_info info = { .code = code,
+						   .errno = errno };
+
+		__audit_seccomp(syscall, &info);
+	}
+}
+
 static inline void audit_seccomp_signal(unsigned long syscall, long signr,
 					int code)
 {
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index b3472f2..db5fc9d 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2426,6 +2426,9 @@ void __audit_seccomp(unsigned long syscall, struct audit_seccomp_info *info)
 	audit_log_task(ab);
 
 	switch (info->code) {
+	case SECCOMP_RET_ERRNO:
+		audit_log_format(ab, " errno=%d", info->errno);
+		break;
 	case SECCOMP_RET_KILL:
 		audit_log_format(ab, " sig=%ld", info->signr);
 		break;
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 54c01b6..e99c566 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -576,9 +576,11 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
 		/* Set low-order bits as an errno, capped at MAX_ERRNO. */
 		if (data > MAX_ERRNO)
 			data = MAX_ERRNO;
+
+		audit_seccomp_errno(this_syscall, data, action);
 		syscall_set_return_value(current, task_pt_regs(current),
 					 -data, 0);
-		goto skip;
+		return -1;
 
 	case SECCOMP_RET_TRAP:
 		/* Show the handler the original registers. */
-- 
2.7.4