Linux sandbox: allow sigaltstack in Android baseline policy.

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

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sandbox/linux/seccomp-bpf-helpers/baseline_policy.h"
 
 #include <errno.h>
 #include <sys/mman.h>
 #include <sys/socket.h>
 #include <sys/syscall.h>
@@ skipping 102 matching lines @@
     // non-ASan builds.
     return Allow();
   }
 #endif  // defined(ADDRESS_SANITIZER) || defined(THREAD_SANITIZER) ||
         // defined(MEMORY_SANITIZER)
 
   if (IsBaselinePolicyAllowed(sysno)) {
     return Allow();
   }
 
-#if defined(__aarch64__)
-  // These are needed for thread creation.
-  // TODO(leecam): Check jln's fix for this and remove these 'allows'.
-  if (sysno == __NR_sigaltstack || sysno == __NR_setpriority)
+#if defined(OS_ANDROID)
+  // Needed for thread creation.
+  if (sysno == __NR_sigaltstack)
     return Allow();
 #endif
 
   if (sysno == __NR_clone) {
     return RestrictCloneToThreadsAndEPERMFork();
   }
 
   if (sysno == __NR_fcntl)
     return RestrictFcntlCommands();
 
@@ skipping 111 matching lines @@
     DCHECK_EQ(syscall(__NR_getpid), current_pid_);
   }
   return EvaluateSyscallImpl(fs_denied_errno_, current_pid_, sysno);
 }
 
 ResultExpr BaselinePolicy::InvalidSyscall() const {
   return CrashSIGSYS();
 }
 
 }  // namespace sandbox.