1 files changed, 110 insertions, 0 deletions
diff --git a/security/sandbox/linux/SandboxHooks.cpp b/security/sandbox/linux/SandboxHooks.cpp
new file mode 100644
index 0000000000..be1a9b1541
--- /dev/null
+++ b/security/sandbox/linux/SandboxHooks.cpp
@@ -0,0 +1,110 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Atomics.h"
+#include "mozilla/Types.h"
+
+#include <dlfcn.h>
+#include <signal.h>
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/inotify.h>
+#ifdef MOZ_X11
+#  include <X11/Xlib.h>
+#endif
+
+// Signal number used to enable seccomp on each thread.
+extern mozilla::Atomic<int> gSeccompTsyncBroadcastSignum;
+
+static bool SigSetNeedsFixup(const sigset_t* aSet) {
+  int tsyncSignum = gSeccompTsyncBroadcastSignum;
+
+  return aSet != nullptr &&
+         (sigismember(aSet, SIGSYS) ||
+          (tsyncSignum != 0 && sigismember(aSet, tsyncSignum)));
+}
+
+static void SigSetFixup(sigset_t* aSet) {
+  int tsyncSignum = gSeccompTsyncBroadcastSignum;
+  int rv = sigdelset(aSet, SIGSYS);
+  MOZ_RELEASE_ASSERT(rv == 0);
+  if (tsyncSignum != 0) {
+    rv = sigdelset(aSet, tsyncSignum);
+    MOZ_RELEASE_ASSERT(rv == 0);
+  }
+}
+
+// This file defines a hook for sigprocmask() and pthread_sigmask().
+// Bug 1176099: some threads block SIGSYS signal which breaks our seccomp-bpf
+// sandbox. To avoid this, we intercept the call and remove SIGSYS.
+//
+// ENOSYS indicates an error within the hook function itself.
+static int HandleSigset(int (*aRealFunc)(int, const sigset_t*, sigset_t*),
+                        int aHow, const sigset_t* aSet, sigset_t* aOldSet,
+                        bool aUseErrno) {
+  if (!aRealFunc) {
+    if (aUseErrno) {
+      errno = ENOSYS;
+      return -1;
+    }
+
+    return ENOSYS;
+  }
+
+  // Avoid unnecessary work
+  if (aHow == SIG_UNBLOCK || !SigSetNeedsFixup(aSet)) {
+    return aRealFunc(aHow, aSet, aOldSet);
+  }
+
+  sigset_t newSet = *aSet;
+  SigSetFixup(&newSet);
+  return aRealFunc(aHow, &newSet, aOldSet);
+}
+
+extern "C" MOZ_EXPORT int sigprocmask(int how, const sigset_t* set,
+                                      sigset_t* oldset) {
+  static auto sRealFunc =
+      (int (*)(int, const sigset_t*, sigset_t*))dlsym(RTLD_NEXT, "sigprocmask");
+
+  return HandleSigset(sRealFunc, how, set, oldset, true);
+}
+
+extern "C" MOZ_EXPORT int pthread_sigmask(int how, const sigset_t* set,
+                                          sigset_t* oldset) {
+  static auto sRealFunc = (int (*)(int, const sigset_t*, sigset_t*))dlsym(
+      RTLD_NEXT, "pthread_sigmask");
+
+  return HandleSigset(sRealFunc, how, set, oldset, false);
+}
+
+extern "C" MOZ_EXPORT int sigaction(int signum, const struct sigaction* act,
+                                    struct sigaction* oldact) {
+  static auto sRealFunc =
+      (int (*)(int, const struct sigaction*, struct sigaction*))dlsym(
+          RTLD_NEXT, "sigaction");
+
+  if (!sRealFunc) {
+    errno = ENOSYS;
+    return -1;
+  }
+
+  if (act == nullptr || !SigSetNeedsFixup(&act->sa_mask)) {
+    return sRealFunc(signum, act, oldact);
+  }
+
+  struct sigaction newact = *act;
+  SigSetFixup(&newact.sa_mask);
+  return sRealFunc(signum, &newact, oldact);
+}
+
+extern "C" MOZ_EXPORT int inotify_init(void) { return inotify_init1(0); }
+
+extern "C" MOZ_EXPORT int inotify_init1(int flags) {
+  errno = ENOSYS;
+  return -1;
+}