api: Add support for SCMP_ACT_KILL_PROCESS

This patch adds support for killing the entire process via
the SCMP_ACT_KILL_PROCESS action.  To maintain backward
compatibility, SCMP_ACT_KILL defaults to SCMP_ACT_KILL_THREAD.
Support for KILL_PROCESS was added into the Linux kernel in
v4.14.

This addresses GitHub Issue #96 - RFE: add support for
SECCOMP_RET_KILL_PROCESS

Signed-off-by: Tom Hromatka <[email protected]>
[PM: minor comment tweak in seccomp.h.in]
Signed-off-by: Paul Moore <[email protected]>

Author: drakenclimber

doc/man/man3/seccomp_init.3

@@ -52,6 +52,10 @@ The thread will be terminated by the kernel with SIGSYS when it calls a syscall
 that does not match any of the configured seccomp filter rules.  The thread
 will not be able to catch the signal.
 .TP
+.B SCMP_ACT_KILL_PROCESS
+The entire process will be terminated by the kernel with SIGSYS when it calls a
+syscall that does not match any of the configured seccomp filter rules.
+.TP
 .B SCMP_ACT_TRAP
 The thread will be sent a SIGSYS signal when it calls a syscall that does not
 match any of the configured seccomp filter rules.  It may catch this and change

doc/man/man3/seccomp_rule_add.3

@@ -111,6 +111,10 @@ values are as follows:
 The thread will be killed by the kernel when it calls a syscall that matches
 the filter rule.
 .TP
+.B SCMP_ACT_KILL_PROCESS
+The process will be killed by the kernel when it calls a syscall that matches
+the filter rule.
+.TP
 .B SCMP_ACT_TRAP
 The thread will throw a SIGSYS signal when it calls a syscall that matches the
 filter rule.

include/seccomp.h.in

@@ -244,7 +244,15 @@ struct scmp_arg_cmp {
 /**
  * Kill the process
  */
-#define SCMP_ACT_KILL		0x00000000U
+#define SCMP_ACT_KILL_PROCESS	0x80000000U
+/**
+ * Kill the thread
+ */
+#define SCMP_ACT_KILL_THREAD	0x00000000U
+/**
+ * Kill the thread, defined for backward compatibility
+ */
+#define SCMP_ACT_KILL		SCMP_ACT_KILL_THREAD
 /**
  * Throw a SIGSYS signal
  */
@@ -297,6 +305,7 @@ const struct scmp_version *seccomp_version(void);
  *      uses the seccomp(2) syscall instead of the prctl(2) syscall
  *  3 : support for the SCMP_FLTATR_CTL_LOG filter attribute
  *      support for the SCMP_ACT_LOG action
+ *      support for the SCMP_ACT_KILL_PROCESS action
  *
  */
 unsigned int seccomp_api_get(void);

src/api.c

@@ -135,18 +135,21 @@ API int seccomp_api_set(unsigned int level)
 		sys_set_seccomp_flag(SECCOMP_FILTER_FLAG_TSYNC, false);
 		sys_set_seccomp_flag(SECCOMP_FILTER_FLAG_LOG, false);
 		sys_set_seccomp_action(SCMP_ACT_LOG, false);
+		sys_set_seccomp_action(SCMP_ACT_KILL_PROCESS, false);
 		break;
 	case 2:
 		sys_set_seccomp_syscall(true);
 		sys_set_seccomp_flag(SECCOMP_FILTER_FLAG_TSYNC, true);
 		sys_set_seccomp_flag(SECCOMP_FILTER_FLAG_LOG, false);
 		sys_set_seccomp_action(SCMP_ACT_LOG, false);
+		sys_set_seccomp_action(SCMP_ACT_KILL_PROCESS, false);
 		break;
 	case 3:
 		sys_set_seccomp_syscall(true);
 		sys_set_seccomp_flag(SECCOMP_FILTER_FLAG_TSYNC, true);
 		sys_set_seccomp_flag(SECCOMP_FILTER_FLAG_LOG, true);
 		sys_set_seccomp_action(SCMP_ACT_LOG, true);
+		sys_set_seccomp_action(SCMP_ACT_KILL_PROCESS, true);
 		break;
 	default:
 		return -EINVAL;

src/gen_pfc.c

@@ -35,6 +35,7 @@
 #include "db.h"
 #include "gen_pfc.h"
 #include "helper.h"
+#include "system.h"
 
 struct pfc_sys_list {
 	struct db_sys_list *sys;
@@ -117,8 +118,11 @@ static void _pfc_arg(FILE *fds,
  */
 static void _pfc_action(FILE *fds, uint32_t action)
 {
-	switch (action & 0xffff0000) {
-	case SCMP_ACT_KILL:
+	switch (action & SECCOMP_RET_ACTION_FULL) {
+	case SCMP_ACT_KILL_PROCESS:
+		fprintf(fds, "action KILL_PROCESS;\n");
+		break;
+	case SCMP_ACT_KILL_THREAD:
 		fprintf(fds, "action KILL;\n");
 		break;
 	case SCMP_ACT_TRAP:

src/python/libseccomp.pxd

@@ -69,6 +69,7 @@ cdef extern from "seccomp.h":
         SCMP_CMP_MASKED_EQ
 
     cdef enum:
+        SCMP_ACT_KILL_PROCESS
         SCMP_ACT_KILL
         SCMP_ACT_TRAP
         SCMP_ACT_LOG

src/python/seccomp.pyx

@@ -29,7 +29,8 @@ based filtering interface that should be familiar to, and easily adopted
 by application developers.
 
 Filter action values:
-    KILL - kill the process
+    KILL_PROCESS - kill the process
+    KILL - kill the thread
     LOG - allow the syscall to be executed after the action has been logged
     ALLOW - allow the syscall to execute
     TRAP - a SIGSYS signal will be thrown
@@ -94,6 +95,7 @@ def c_str(string):
     else:
         return bytes(string, "ascii")
 
+KILL_PROCESS = libseccomp.SCMP_ACT_KILL_PROCESS
 KILL = libseccomp.SCMP_ACT_KILL
 TRAP = libseccomp.SCMP_ACT_TRAP
 LOG = libseccomp.SCMP_ACT_LOG
@@ -545,7 +547,8 @@ cdef class SyscallFilter:
         """ Add a new rule to filter.
 
         Arguments:
-        action - the rule action: KILL, TRAP, ERRNO(), TRACE(), LOG, or ALLOW
+        action - the rule action: KILL_PROCESS, KILL, TRAP, ERRNO(), TRACE(),
+                 LOG, or ALLOW
         syscall - the syscall name or number
         args - variable number of Arg objects
 
@@ -627,7 +630,8 @@ cdef class SyscallFilter:
         """ Add a new rule to filter.
 
         Arguments:
-        action - the rule action: KILL, TRAP, ERRNO(), TRACE(), LOG, or ALLOW
+        action - the rule action: KILL_PROCESS, KILL, TRAP, ERRNO(), TRACE(),
+                 LOG, or ALLOW
         syscall - the syscall name or number
         args - variable number of Arg objects
 

src/system.c

@@ -43,6 +43,7 @@ static int _support_seccomp_syscall = -1;
 static int _support_seccomp_flag_tsync = -1;
 static int _support_seccomp_flag_log = -1;
 static int _support_seccomp_action_log = -1;
+static int _support_seccomp_kill_process = -1;
 
 /**
  * Check to see if the seccomp() syscall is supported
@@ -123,7 +124,18 @@ void sys_set_seccomp_syscall(bool enable)
  */
 int sys_chk_seccomp_action(uint32_t action)
 {
-	if (action == SCMP_ACT_KILL) {
+	if (action == SCMP_ACT_KILL_PROCESS) {
+		if (_support_seccomp_kill_process < 0) {
+			if (sys_chk_seccomp_syscall() == 1 &&
+			    syscall(_nr_seccomp, SECCOMP_GET_ACTION_AVAIL, 0,
+				    &action) == 0)
+				_support_seccomp_kill_process = 1;
+			else
+				_support_seccomp_kill_process = 0;
+		}
+
+		return _support_seccomp_kill_process;
+	} else if (action == SCMP_ACT_KILL_THREAD) {
 		return 1;
 	} else if (action == SCMP_ACT_TRAP) {
 		return 1;
@@ -162,6 +174,8 @@ void sys_set_seccomp_action(uint32_t action, bool enable)
 {
 	if (action == SCMP_ACT_LOG)
 		_support_seccomp_action_log = (enable ? 1 : 0);
+	else if (action == SCMP_ACT_KILL_PROCESS)
+		_support_seccomp_kill_process = (enable ? 1 : 0);
 }
 
 /**

src/system.h

@@ -55,13 +55,16 @@ struct db_filter_col;
  * The ordering ensures that a min_t() over composed return values always
  * selects the least permissive choice.
  */
-#define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
+#define SECCOMP_RET_KILL_PROCESS 0x80000000U /* kill the process immediately */
+#define SECCOMP_RET_KILL_THREAD	0x00000000U /* kill the thread immediately */
+#define SECCOMP_RET_KILL	SECCOMP_RET_KILL_THREAD /* default to killing the thread */
 #define SECCOMP_RET_TRAP	0x00030000U /* disallow and force a SIGSYS */
 #define SECCOMP_RET_ERRNO	0x00050000U /* returns an errno */
 #define SECCOMP_RET_TRACE	0x7ff00000U /* pass to a tracer or disallow */
 #define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
 
 /* Masks for the return value sections. */
+#define SECCOMP_RET_ACTION_FULL 0xffff0000U
 #define SECCOMP_RET_ACTION	0x7fff0000U
 #define SECCOMP_RET_DATA	0x0000ffffU
 
@@ -118,6 +121,13 @@ typedef struct sock_filter bpf_instr_raw;
 #define SECCOMP_RET_LOG		0x7ffc0000U /* allow after logging */
 #endif
 
+/* SECCOMP_RET_ACTION_FULL was added in kernel v4.14.  It may not be
+ * defined on older kernels
+ */
+#ifndef SECCOMP_RET_ACTION_FULL
+#define SECCOMP_RET_ACTION_FULL 0xffff0000U
+#endif
+
 int sys_chk_seccomp_syscall(void);
 void sys_set_seccomp_syscall(bool enable);
 

tools/bpf.h

@@ -56,11 +56,14 @@ struct sock_filter {
 typedef struct sock_filter bpf_instr_raw;
 
 /* seccomp return masks */
+#define SECCOMP_RET_ACTION_FULL 0xffff0000U
 #define SECCOMP_RET_ACTION	0x7fff0000U
 #define SECCOMP_RET_DATA	0x0000ffffU
 
 /* seccomp action values */
-#define SECCOMP_RET_KILL	0x00000000U
+#define SECCOMP_RET_KILL_PROCESS 0x80000000U
+#define SECCOMP_RET_KILL_THREAD 0x00000000U
+#define SECCOMP_RET_KILL	SECCOMP_RET_KILL_THREAD
 #define SECCOMP_RET_TRAP	0x00030000U
 #define SECCOMP_RET_ERRNO	0x00050000U
 #define SECCOMP_RET_TRACE	0x7ff00000U