kernel: extend seccomp with a LOG action

Signed-off-by: John Crispin <blogic@openwrt.org>

SVN-Revision: 45007

target/linux/generic/patches-3.18/999-seccomp_log.patch

@@ -0,0 +1,34 @@
+--- a/kernel/seccomp.c
++++ b/kernel/seccomp.c
+@@ -614,6 +614,7 @@
+ #ifdef CONFIG_SECCOMP_FILTER
+ static u32 __seccomp_phase1_filter(int this_syscall, struct seccomp_data *sd)
+ {
++	char name[sizeof(current->comm)];
+ 	u32 filter_ret, action;
+ 	int data;
+ 
+@@ -644,6 +645,13 @@
+ 	case SECCOMP_RET_TRACE:
+ 		return filter_ret;  /* Save the rest for phase 2. */
+ 
++	case SECCOMP_RET_LOG:
++		get_task_comm(name, current);
++		pr_err_ratelimited("seccomp: %s [%u] tried to call non-whitelisted syscall: %d\n", name, current->pid, this_syscall);
++		syscall_set_return_value(current, task_pt_regs(current),
++					 -data, 0);
++		goto skip;
++
+ 	case SECCOMP_RET_ALLOW:
+ 		return SECCOMP_PHASE1_OK;
+ 
+--- a/include/uapi/linux/seccomp.h
++++ b/include/uapi/linux/seccomp.h
+@@ -28,6 +28,7 @@
+ #define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
+ #define SECCOMP_RET_TRAP	0x00030000U /* disallow and force a SIGSYS */
+ #define SECCOMP_RET_ERRNO	0x00050000U /* returns an errno */
++#define SECCOMP_RET_LOG		0x00070000U /* allow + logline */
+ #define SECCOMP_RET_TRACE	0x7ff00000U /* pass to a tracer or disallow */
+ #define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
+