From e142aa87d663a95d1bbab41543aafce24eced707 Mon Sep 17 00:00:00 2001 From: Mark Mentovai Date: Fri, 7 Apr 2017 17:14:21 -0400 Subject: [PATCH] linux: Fix crashpad_util_test ScopedPtraceAttach.* with the Yama LSM When Yama is enabled and /proc/sys/kernel/yama/ptrace_scope is set to 1 (YAMA_SCOPE_RELATIONAL), for a child to ptrace() its parent, the parent must first call prctl(PR_SET_PTRACER, child_pid, ...). Bug: crashpad:30 Test: crashpad_util_test ScopedPtraceAttach.* Change-Id: Ic85e8551259f17f372b2362887e7701b833b4cb4 Reviewed-on: https://chromium-review.googlesource.com/472006 Reviewed-by: Joshua Peraza --- compat/android/linux/prctl.h | 25 ++++++++ util/linux/scoped_ptrace_attach_test.cc | 82 ++++++++++++++++++++++--- 2 files changed, 98 insertions(+), 9 deletions(-) create mode 100644 compat/android/linux/prctl.h diff --git a/compat/android/linux/prctl.h b/compat/android/linux/prctl.h new file mode 100644 index 00000000..046f900f --- /dev/null +++ b/compat/android/linux/prctl.h @@ -0,0 +1,25 @@ +// Copyright 2017 The Crashpad Authors. All rights reserved. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef CRASHPAD_COMPAT_ANDROID_LINUX_PRCTL_H_ +#define CRASHPAD_COMPAT_ANDROID_LINUX_PRCTL_H_ + +#include_next + +// Android 5.0.0 (API 21) NDK +#if !defined(PR_SET_PTRACER) +#define PR_SET_PTRACER 0x59616d61 +#endif + +#endif // CRASHPAD_COMPAT_ANDROID_LINUX_PRCTL_H_ diff --git a/util/linux/scoped_ptrace_attach_test.cc b/util/linux/scoped_ptrace_attach_test.cc index 3f7c1363..99072e4c 100644 --- a/util/linux/scoped_ptrace_attach_test.cc +++ b/util/linux/scoped_ptrace_attach_test.cc @@ -14,6 +14,8 @@ #include "util/linux/scoped_ptrace_attach.h" +#include +#include #include #include @@ -26,6 +28,40 @@ namespace crashpad { namespace test { namespace { +class ScopedPrSetPtracer { + public: + explicit ScopedPrSetPtracer(pid_t pid) { + // PR_SET_PTRACER is only supported if the Yama Linux security module (LSM) + // is enabled. Otherwise, this prctl() call fails with EINVAL. See + // linux-4.9.20/security/yama/yama_lsm.c yama_task_prctl() and + // linux-4.9.20/kernel/sys.c [sys_]prctl(). + // + // If Yama is not enabled, the default ptrace restrictions should be + // sufficient for these tests. + // + // If Yama is enabled, then /proc/sys/kernel/yama/ptrace_scope must be 0 + // (YAMA_SCOPE_DISABLED, in which case this prctl() is not necessary) or 1 + // (YAMA_SCOPE_RELATIONAL) for these tests to succeed. If it is 2 + // (YAMA_SCOPE_CAPABILITY) then the test requires CAP_SYS_PTRACE, and if it + // is 3 (YAMA_SCOPE_NO_ATTACH), these tests will fail. + success_ = prctl(PR_SET_PTRACER, pid, 0, 0, 0) == 0; + if (!success_) { + EXPECT_EQ(errno, EINVAL) << ErrnoMessage("prctl"); + } + } + + ~ScopedPrSetPtracer() { + if (success_) { + EXPECT_EQ(prctl(PR_SET_PTRACER, 0, 0, 0, 0), 0) << ErrnoMessage("prctl"); + } + } + + private: + bool success_; + + DISALLOW_COPY_AND_ASSIGN(ScopedPrSetPtracer); +}; + class AttachTest : public Multiprocess { public: AttachTest() : Multiprocess() {} @@ -45,21 +81,31 @@ class AttachToChildTest : public AttachTest { private: void MultiprocessParent() override { + // Wait for the child to set the parent as its ptracer. + char c; + CheckedReadFileExactly(ReadPipeHandle(), &c, sizeof(c)); + pid_t pid = ChildPID(); ASSERT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), -1); - EXPECT_EQ(errno, ESRCH); + EXPECT_EQ(errno, ESRCH) << ErrnoMessage("ptrace"); ScopedPtraceAttach attachment; ASSERT_EQ(attachment.ResetAttach(pid), true); - EXPECT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), kWord); + EXPECT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), kWord) + << ErrnoMessage("ptrace"); attachment.Reset(); ASSERT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), -1); - EXPECT_EQ(errno, ESRCH); + EXPECT_EQ(errno, ESRCH) << ErrnoMessage("ptrace"); } void MultiprocessChild() override { + ScopedPrSetPtracer set_ptracer(getppid()); + + char c = '\0'; + CheckedWriteFile(WritePipeHandle(), &c, sizeof(c)); + CheckedReadFileAtEOF(ReadPipeHandle()); } @@ -78,22 +124,31 @@ class AttachToParentResetTest : public AttachTest { private: void MultiprocessParent() override { + ScopedPrSetPtracer set_ptracer(ChildPID()); + char c = '\0'; + CheckedWriteFile(WritePipeHandle(), &c, sizeof(c)); + CheckedReadFileAtEOF(ReadPipeHandle()); } void MultiprocessChild() override { + // Wait for the parent to set the child as its ptracer. + char c; + CheckedReadFileExactly(ReadPipeHandle(), &c, sizeof(c)); + pid_t pid = getppid(); ASSERT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), -1); - EXPECT_EQ(errno, ESRCH); + EXPECT_EQ(errno, ESRCH) << ErrnoMessage("ptrace"); ScopedPtraceAttach attachment; ASSERT_EQ(attachment.ResetAttach(pid), true); - EXPECT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), kWord); + EXPECT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), kWord) + << ErrnoMessage("ptrace"); attachment.Reset(); ASSERT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), -1); - EXPECT_EQ(errno, ESRCH); + EXPECT_EQ(errno, ESRCH) << ErrnoMessage("ptrace"); } DISALLOW_COPY_AND_ASSIGN(AttachToParentResetTest); @@ -111,20 +166,29 @@ class AttachToParentDestructorTest : public AttachTest { private: void MultiprocessParent() override { + ScopedPrSetPtracer set_ptracer(ChildPID()); + char c = '\0'; + CheckedWriteFile(WritePipeHandle(), &c, sizeof(c)); + CheckedReadFileAtEOF(ReadPipeHandle()); } void MultiprocessChild() override { + // Wait for the parent to set the child as its ptracer. + char c; + CheckedReadFileExactly(ReadPipeHandle(), &c, sizeof(c)); + pid_t pid = getppid(); ASSERT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), -1); - EXPECT_EQ(errno, ESRCH); + EXPECT_EQ(errno, ESRCH) << ErrnoMessage("ptrace"); { ScopedPtraceAttach attachment; ASSERT_EQ(attachment.ResetAttach(pid), true); - EXPECT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), kWord); + EXPECT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), kWord) + << ErrnoMessage("ptrace"); } ASSERT_EQ(ptrace(PTRACE_PEEKDATA, pid, &kWord, nullptr), -1); - EXPECT_EQ(errno, ESRCH); + EXPECT_EQ(errno, ESRCH) << ErrnoMessage("ptrace"); } DISALLOW_COPY_AND_ASSIGN(AttachToParentDestructorTest);