Linux sandbox: restrict *kill to the current process.

sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc

Index: sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
diff --git a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
index 47c99892996bd755904efd262232f3a393bf1ddb..c4a6f92c01d423521aee83ffcaf2e4cc35f4e82a 100644
--- a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
+++ b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
@@ -17,6 +17,7 @@
 #define SECCOMP_MESSAGE_CLONE_CONTENT "clone() failure"
 #define SECCOMP_MESSAGE_PRCTL_CONTENT "prctl() failure"
 #define SECCOMP_MESSAGE_IOCTL_CONTENT "ioctl() failure"
+#define SECCOMP_MESSAGE_KILL_CONTENT "(tg)kill() failure"
 
 namespace {
 
@@ -147,6 +148,22 @@ intptr_t SIGSYSIoctlFailure(const struct arch_seccomp_data& args,
     _exit(1);
 }
 
+intptr_t SIGSYSKillFailure(const struct arch_seccomp_data& args,
+                           void* /* aux */) {
+   static const char kSeccompKillError[] =
+      __FILE__":**CRASHING**:" SECCOMP_MESSAGE_KILL_CONTENT "\n";
+  WriteToStdErr(kSeccompKillError, sizeof(kSeccompKillError) - 1);
+  // Make "request" volatile so that we can see it on the stack in a minidump.
+  volatile uint64_t pid = args.args[0];
+  volatile char* addr = reinterpret_cast<volatile char*>(pid & 0xFFF);
+  *addr = '\0';
+  // Hit the NULL page if this fails.
+  addr = reinterpret_cast<volatile char*>(pid & 0xFFF);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
 const char* GetErrorMessageContentForTests() {
   return SECCOMP_MESSAGE_COMMON_CONTENT;
 }