mirrors/cosmopolitan
1
0
Fork 0
mirror of https://github.com/jart/cosmopolitan.git synced 2025-05-28 00:02:28 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

Improve stack overflow recovery

Browse source 
It's now possible to use sigaltstack() to recover from stack overflows
on Windows. Several bugs in sigaltstack() have been fixed, for all our
supported platforms. There's a newer better example showing how to use
this, along with three independent unit tests just to further showcase
the various techniques.
This commit is contained in:
Justine Tunney 2023-10-04 07:07:43 -07:00
parent 1694edf85c
commit 4631d34d0d
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
24 changed files with 590 additions and 274 deletions
Download patch file Download diff file Expand all files Collapse all files

2
test/libc/calls/pledge_test.c
View file

@ -552,6 +552,8 @@ TEST(pledge_openbsd, execpromisesIsNull_letsItDoAnything) {
}
EXPECT_NE(-1, wait(&ws));
EXPECT_TRUE(WIFEXITED(ws));
EXPECT_FALSE(WIFSIGNALED(ws));
EXPECT_EQ(0, WTERMSIG(ws));
EXPECT_EQ(3, WEXITSTATUS(ws));
}

52
test/libc/thread/pthread_create_test.c
View file

@ -255,58 +255,6 @@ TEST(pthread_cleanup, pthread_normal) {
ASSERT_TRUE(g_cleanup2);
}
////////////////////////////////////////////////////////////////////////////////
jmp_buf recover;
volatile bool smashed_stack;
void CrashHandler(int sig, siginfo_t *si, void *ctx) {
kprintf("kprintf avoids overflowing %G %p\n", si->si_signo, si->si_addr);
smashed_stack = true;
ASSERT_TRUE(__is_stack_overflow(si, ctx));
longjmp(recover, 123);
}
int StackOverflow(int f(), int n) {
if (n < INT_MAX) {
return f(f, n + 1) - 1;
} else {
return INT_MAX;
}
}
int (*pStackOverflow)(int (*)(), int) = StackOverflow;
void *MyPosixThread(void *arg) {
int jumpcode;
struct sigaction sa, o1, o2;
struct sigaltstack ss;
ss.ss_flags = 0;
ss.ss_size = sysconf(_SC_MINSIGSTKSZ) + 4096;
ss.ss_sp = gc(malloc(ss.ss_size));
ASSERT_SYS(0, 0, sigaltstack(&ss, 0));
sa.sa_flags = SA_SIGINFO | SA_ONSTACK; // <-- important
sigemptyset(&sa.sa_mask);
sa.sa_sigaction = CrashHandler;
sigaction(SIGBUS, &sa, &o1);
sigaction(SIGSEGV, &sa, &o2);
if (!(jumpcode = setjmp(recover))) {
exit(pStackOverflow(pStackOverflow, 0));
}
ASSERT_EQ(123, jumpcode);
sigaction(SIGSEGV, &o2, 0);
sigaction(SIGBUS, &o1, 0);
return 0;
}
TEST(cosmo, altstack_thread) {
pthread_t th;
if (IsWindows()) return;
pthread_create(&th, 0, MyPosixThread, 0);
pthread_join(th, 0);
ASSERT_TRUE(smashed_stack);
}
////////////////////////////////////////////////////////////////////////////////
// BENCHMARKS

104
test/libc/thread/stackoverflow1_test.c Normal file
View file

@ -0,0 +1,104 @@
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2023 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/struct/rlimit.h"
#include "libc/calls/struct/sigaction.h"
#include "libc/calls/struct/sigaltstack.h"
#include "libc/calls/struct/siginfo.h"
#include "libc/dce.h"
#include "libc/intrin/kprintf.h"
#include "libc/limits.h"
#include "libc/mem/gc.internal.h"
#include "libc/mem/mem.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/sysconf.h"
#include "libc/sysv/consts/rlimit.h"
#include "libc/sysv/consts/sa.h"
#include "libc/sysv/consts/sig.h"
#include "libc/sysv/consts/ss.h"
#include "libc/testlib/testlib.h"
#include "libc/thread/thread.h"
/**
* stack overflow recovery technique #1
* overflow the gigantic main process stack
* simple but it can upset kernels / libraries
*/
jmp_buf recover;
volatile bool smashed_stack;
void CrashHandler(int sig, siginfo_t *si, void *ctx) {
struct sigaltstack ss;
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(SS_ONSTACK, ss.ss_flags);
kprintf("kprintf avoids overflowing %G %p\n", si->si_signo, si->si_addr);
smashed_stack = true;
ASSERT_TRUE(__is_stack_overflow(si, ctx));
longjmp(recover, 123);
}
void SetUp(void) {
// tune down the main process's stack size to a reasonable amount
// some operating systems, e.g. freebsd, will do things like have
// 500mb RLIMIT_STACK by default, even on machines with 400mb RAM
struct rlimit rl = {2 * 1024 * 1024, 2 * 1024 * 1024};
if (!IsWindows()) setrlimit(RLIMIT_STACK, &rl);
// set up the signal handler and alternative stack
struct sigaction sa;
struct sigaltstack ss;
ss.ss_flags = 0;
ss.ss_size = sysconf(_SC_MINSIGSTKSZ) + 8192;
ss.ss_sp = _mapanon(ss.ss_size);
ASSERT_SYS(0, 0, sigaltstack(&ss, 0));
sa.sa_flags = SA_SIGINFO | SA_ONSTACK; // <-- important
sigemptyset(&sa.sa_mask);
sa.sa_sigaction = CrashHandler;
sigaction(SIGBUS, &sa, 0);
sigaction(SIGSEGV, &sa, 0);
}
int StackOverflow(int f(), int n) {
if (n < INT_MAX) {
return f(f, n + 1) - 1;
} else {
return INT_MAX;
}
}
int (*pStackOverflow)(int (*)(), int) = StackOverflow;
TEST(stackoverflow, standardStack_altStack_process_longjmp) {
int jumpcode;
if (!(jumpcode = setjmp(recover))) {
exit(pStackOverflow(pStackOverflow, 0));
}
ASSERT_EQ(123, jumpcode);
ASSERT_TRUE(smashed_stack);
// here's where longjmp() gets us into trouble
struct sigaltstack ss;
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
if (IsXnu() || IsNetbsd()) {
ASSERT_EQ(SS_ONSTACK, ss.ss_flags); // wut
} else {
ASSERT_EQ(0, ss.ss_flags);
}
}

105
test/libc/thread/stackoverflow2_test.c Normal file
View file

@ -0,0 +1,105 @@
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2023 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/struct/sigaction.h"
#include "libc/calls/struct/sigaltstack.h"
#include "libc/calls/struct/siginfo.h"
#include "libc/dce.h"
#include "libc/intrin/kprintf.h"
#include "libc/limits.h"
#include "libc/mem/gc.internal.h"
#include "libc/mem/mem.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/sysconf.h"
#include "libc/sysv/consts/sa.h"
#include "libc/sysv/consts/sig.h"
#include "libc/sysv/consts/ss.h"
#include "libc/testlib/testlib.h"
#include "libc/thread/thread.h"
/**
* stack overflow recovery technique #2
* longjmp out of signal back into thread
* simple but it can upset kernels / libraries
*/
jmp_buf recover;
volatile bool smashed_stack;
void CrashHandler(int sig, siginfo_t *si, void *ctx) {
struct sigaltstack ss;
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(SS_ONSTACK, ss.ss_flags);
kprintf("kprintf avoids overflowing %G %p\n", si->si_signo, si->si_addr);
smashed_stack = true;
ASSERT_TRUE(__is_stack_overflow(si, ctx));
longjmp(recover, 123);
}
int StackOverflow(int f(), int n) {
if (n < INT_MAX) {
return f(f, n + 1) - 1;
} else {
return INT_MAX;
}
}
int (*pStackOverflow)(int (*)(), int) = StackOverflow;
void *MyPosixThread(void *arg) {
int jumpcode;
struct sigaction sa, o1, o2;
struct sigaltstack ss;
ss.ss_flags = 0;
ss.ss_size = sysconf(_SC_MINSIGSTKSZ) + 4096;
ss.ss_sp = gc(malloc(ss.ss_size));
ASSERT_SYS(0, 0, sigaltstack(&ss, 0));
sa.sa_flags = SA_SIGINFO | SA_ONSTACK; // <-- important
sigemptyset(&sa.sa_mask);
sa.sa_sigaction = CrashHandler;
sigaction(SIGBUS, &sa, &o1);
sigaction(SIGSEGV, &sa, &o2);
if (!(jumpcode = setjmp(recover))) {
exit(pStackOverflow(pStackOverflow, 0));
}
ASSERT_EQ(123, jumpcode);
sigaction(SIGSEGV, &o2, 0);
sigaction(SIGBUS, &o1, 0);
// here's where longjmp() gets us into trouble
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
if (IsXnu() || IsNetbsd()) {
ASSERT_EQ(SS_ONSTACK, ss.ss_flags); // wut
} else {
ASSERT_EQ(0, ss.ss_flags);
}
return 0;
}
TEST(stackoverflow, standardStack_altStack_thread_longjmp) {
pthread_t th;
struct sigaltstack ss;
for (int i = 0; i < 2; ++i) {
smashed_stack = false;
pthread_create(&th, 0, MyPosixThread, 0);
pthread_join(th, 0);
ASSERT_TRUE(smashed_stack);
// this should be SS_DISABLE but ShowCrashReports() creates an alt stack
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(0, ss.ss_flags);
}
}

116
test/libc/thread/stackoverflow3_test.c Normal file
View file

@ -0,0 +1,116 @@
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2023 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/struct/sigaction.h"
#include "libc/calls/struct/sigaltstack.h"
#include "libc/calls/struct/siginfo.h"
#include "libc/calls/struct/ucontext.internal.h"
#include "libc/calls/ucontext.h"
#include "libc/intrin/kprintf.h"
#include "libc/limits.h"
#include "libc/mem/gc.internal.h"
#include "libc/mem/mem.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/sysconf.h"
#include "libc/sysv/consts/sa.h"
#include "libc/sysv/consts/sig.h"
#include "libc/sysv/consts/ss.h"
#include "libc/testlib/testlib.h"
#include "libc/thread/thread.h"
/**
* stack overflow recovery technique #3
* rewrite thread cpu state to call pthread_exit
* this method returns gracefully from signal handlers
* unfortunately it relies on cpu architecture knowledge
*/
volatile bool smashed_stack;
void Exiter(void *rc) {
struct sigaltstack ss;
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(0, ss.ss_flags);
pthread_exit(rc);
}
void CrashHandler(int sig, siginfo_t *si, void *arg) {
ucontext_t *ctx = arg;
struct sigaltstack ss;
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(SS_ONSTACK, ss.ss_flags);
kprintf("kprintf avoids overflowing %G %p\n", si->si_signo, si->si_addr);
smashed_stack = true;
ASSERT_TRUE(__is_stack_overflow(si, ctx));
//
// the backtrace will look like this
//
// 0x000000000042561d: pthread_exit at pthread_exit.c:99
// 0x0000000000418777: Exiter at stackoverflow2_test.c:40
// 0x00000000004186d8: CrashHandler at stackoverflow2_test.c:49
// 0x000000000041872a: StackOverflow at stackoverflow2_test.c:53
// 0x000000000041872a: StackOverflow at stackoverflow2_test.c:53
// 0x000000000041872a: StackOverflow at stackoverflow2_test.c:53
// ...
//
ctx->uc_mcontext.ARG0 = 123;
ctx->uc_mcontext.PC = (long)Exiter;
ctx->uc_mcontext.SP += 32768;
ctx->uc_mcontext.SP &= -16;
ctx->uc_mcontext.SP -= 8;
}
int StackOverflow(int f(), int n) {
if (n < INT_MAX) {
return f(f, n + 1) - 1;
} else {
return INT_MAX;
}
}
int (*pStackOverflow)(int (*)(), int) = StackOverflow;
void *MyPosixThread(void *arg) {
struct sigaction sa;
struct sigaltstack ss;
ss.ss_flags = 0;
ss.ss_size = sysconf(_SC_MINSIGSTKSZ) + 4096;
ss.ss_sp = gc(malloc(ss.ss_size));
ASSERT_SYS(0, 0, sigaltstack(&ss, 0));
sa.sa_flags = SA_SIGINFO | SA_ONSTACK; // <-- important
sigemptyset(&sa.sa_mask);
sa.sa_sigaction = CrashHandler;
sigaction(SIGBUS, &sa, 0);
sigaction(SIGSEGV, &sa, 0);
exit(pStackOverflow(pStackOverflow, 0));
return 0;
}
TEST(stackoverflow, standardStack_altStack_thread_teleport) {
void *res;
pthread_t th;
struct sigaltstack ss;
smashed_stack = false;
pthread_create(&th, 0, MyPosixThread, 0);
pthread_join(th, &res);
ASSERT_EQ((void *)123L, res);
ASSERT_TRUE(smashed_stack);
// this should be SS_DISABLE but ShowCrashReports() creates an alt stack
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(0, ss.ss_flags);
}