1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
3 /* This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
5 * You can obtain one at http://mozilla.org/MPL/2.0/. */
6
7 #include "mozilla/Atomics.h"
8 #include "mozilla/Types.h"
9
10 #include <dlfcn.h>
11 #include <signal.h>
12 #include <errno.h>
13 #include <signal.h>
14 #include <stdio.h>
15 #include <stdlib.h>
16 #include <sys/inotify.h>
17 #ifdef MOZ_X11
18 #include <X11/Xlib.h>
19 #endif
20
21 // Signal number used to enable seccomp on each thread.
22 extern mozilla::Atomic<int> gSeccompTsyncBroadcastSignum;
23
SigSetNeedsFixup(const sigset_t * aSet)24 static bool SigSetNeedsFixup(const sigset_t* aSet) {
25 int tsyncSignum = gSeccompTsyncBroadcastSignum;
26
27 return aSet != nullptr &&
28 (sigismember(aSet, SIGSYS) ||
29 (tsyncSignum != 0 && sigismember(aSet, tsyncSignum)));
30 }
31
SigSetFixup(sigset_t * aSet)32 static void SigSetFixup(sigset_t* aSet) {
33 int tsyncSignum = gSeccompTsyncBroadcastSignum;
34 int rv = sigdelset(aSet, SIGSYS);
35 MOZ_RELEASE_ASSERT(rv == 0);
36 if (tsyncSignum != 0) {
37 rv = sigdelset(aSet, tsyncSignum);
38 MOZ_RELEASE_ASSERT(rv == 0);
39 }
40 }
41
42 // This file defines a hook for sigprocmask() and pthread_sigmask().
43 // Bug 1176099: some threads block SIGSYS signal which breaks our seccomp-bpf
44 // sandbox. To avoid this, we intercept the call and remove SIGSYS.
45 //
46 // ENOSYS indicates an error within the hook function itself.
HandleSigset(int (* aRealFunc)(int,const sigset_t *,sigset_t *),int aHow,const sigset_t * aSet,sigset_t * aOldSet,bool aUseErrno)47 static int HandleSigset(int (*aRealFunc)(int, const sigset_t*, sigset_t*),
48 int aHow, const sigset_t* aSet, sigset_t* aOldSet,
49 bool aUseErrno) {
50 if (!aRealFunc) {
51 if (aUseErrno) {
52 errno = ENOSYS;
53 return -1;
54 }
55
56 return ENOSYS;
57 }
58
59 // Avoid unnecessary work
60 if (aHow == SIG_UNBLOCK || !SigSetNeedsFixup(aSet)) {
61 return aRealFunc(aHow, aSet, aOldSet);
62 }
63
64 sigset_t newSet = *aSet;
65 SigSetFixup(&newSet);
66 return aRealFunc(aHow, &newSet, aOldSet);
67 }
68
sigprocmask(int how,const sigset_t * set,sigset_t * oldset)69 extern "C" MOZ_EXPORT int sigprocmask(int how, const sigset_t* set,
70 sigset_t* oldset) {
71 static auto sRealFunc =
72 (int (*)(int, const sigset_t*, sigset_t*))dlsym(RTLD_NEXT, "sigprocmask");
73
74 return HandleSigset(sRealFunc, how, set, oldset, true);
75 }
76
pthread_sigmask(int how,const sigset_t * set,sigset_t * oldset)77 extern "C" MOZ_EXPORT int pthread_sigmask(int how, const sigset_t* set,
78 sigset_t* oldset) {
79 static auto sRealFunc = (int (*)(int, const sigset_t*, sigset_t*))dlsym(
80 RTLD_NEXT, "pthread_sigmask");
81
82 return HandleSigset(sRealFunc, how, set, oldset, false);
83 }
84
sigaction(int signum,const struct sigaction * act,struct sigaction * oldact)85 extern "C" MOZ_EXPORT int sigaction(int signum, const struct sigaction* act,
86 struct sigaction* oldact) {
87 static auto sRealFunc =
88 (int (*)(int, const struct sigaction*, struct sigaction*))dlsym(
89 RTLD_NEXT, "sigaction");
90
91 if (!sRealFunc) {
92 errno = ENOSYS;
93 return -1;
94 }
95
96 if (act == nullptr || !SigSetNeedsFixup(&act->sa_mask)) {
97 return sRealFunc(signum, act, oldact);
98 }
99
100 struct sigaction newact = *act;
101 SigSetFixup(&newact.sa_mask);
102 return sRealFunc(signum, &newact, oldact);
103 }
104
inotify_init(void)105 extern "C" MOZ_EXPORT int inotify_init(void) { return inotify_init1(0); }
106
inotify_init1(int flags)107 extern "C" MOZ_EXPORT int inotify_init1(int flags) {
108 errno = ENOSYS;
109 return -1;
110 }
111