2023-12-21 18:59:19 +00:00
|
|
|
/* Fortify check for wprintf.
|
2024-01-01 18:12:26 +00:00
|
|
|
Copyright (C) 2023-2024 Free Software Foundation, Inc.
|
2023-12-21 18:59:19 +00:00
|
|
|
Copyright The GNU Toolchain Authors.
|
|
|
|
|
This file is part of the GNU C Library.
|
|
|
|
|
|
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
|
|
|
modify it under the terms of the GNU Lesser General Public
|
|
|
|
|
License as published by the Free Software Foundation; either
|
|
|
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
|
|
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
|
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
|
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
|
|
|
Lesser General Public License for more details.
|
|
|
|
|
|
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
|
|
|
License along with the GNU C Library; if not, see
|
|
|
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
|
|
|
|
|
|
#include <setjmp.h>
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
#include <unistd.h>
|
|
|
|
|
|
|
|
|
|
#include <support/support.h>
|
|
|
|
|
|
|
|
|
|
static volatile int chk_fail_ok;
|
|
|
|
|
static volatile int ret;
|
stdlib: Make abort/_Exit AS-safe (BZ 26275)
The recursive lock used on abort does not synchronize with a new process
creation (either by fork-like interfaces or posix_spawn ones), nor it
is reinitialized after fork().
Also, the SIGABRT unblock before raise() shows another race condition,
where a fork or posix_spawn() call by another thread, just after the
recursive lock release and before the SIGABRT signal, might create
programs with a non-expected signal mask. With the default option
(without POSIX_SPAWN_SETSIGDEF), the process can see SIG_DFL for
SIGABRT, where it should be SIG_IGN.
To fix the AS-safe, raise() does not change the process signal mask,
and an AS-safe lock is used if a SIGABRT is installed or the process
is blocked or ignored. With the signal mask change removal,
there is no need to use a recursive loc. The lock is also taken on
both _Fork() and posix_spawn(), to avoid the spawn process to see the
abort handler as SIG_DFL.
A read-write lock is used to avoid serialize _Fork and posix_spawn
execution. Both sigaction (SIGABRT) and abort() requires to lock
as writer (since both change the disposition).
The fallback is also simplified: there is no need to use a loop of
ABORT_INSTRUCTION after _exit() (if the syscall does not terminate the
process, the system is broken).
The proposed fix changes how setjmp works on a SIGABRT handler, where
glibc does not save the signal mask. So usage like the below will now
always abort.
static volatile int chk_fail_ok;
static jmp_buf chk_fail_buf;
static void
handler (int sig)
{
if (chk_fail_ok)
{
chk_fail_ok = 0;
longjmp (chk_fail_buf, 1);
}
else
_exit (127);
}
[...]
signal (SIGABRT, handler);
[....]
chk_fail_ok = 1;
if (! setjmp (chk_fail_buf))
{
// Something that can calls abort, like a failed fortify function.
chk_fail_ok = 0;
printf ("FAIL\n");
}
Such cases will need to use sigsetjmp instead.
The _dl_start_profile calls sigaction through _profil, and to avoid
pulling abort() on loader the call is replaced with __libc_sigaction.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>
2024-10-03 18:41:10 +00:00
|
|
|
static sigjmp_buf chk_fail_buf;
|
2023-12-21 18:59:19 +00:00
|
|
|
|
|
|
|
|
static void
|
|
|
|
|
handler (int sig)
|
|
|
|
|
{
|
|
|
|
|
if (chk_fail_ok)
|
|
|
|
|
{
|
|
|
|
|
chk_fail_ok = 0;
|
|
|
|
|
longjmp (chk_fail_buf, 1);
|
|
|
|
|
}
|
|
|
|
|
else
|
|
|
|
|
_exit (127);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static const wchar_t *wstr3 = L"%ls%n%ls%n";
|
|
|
|
|
static const wchar_t *wstr4 = L"Hello, ";
|
|
|
|
|
static const wchar_t *wstr5 = L"World!\n";
|
|
|
|
|
static wchar_t wbuf2[20] = L"%ls";
|
|
|
|
|
|
|
|
|
|
#define WFAIL \
|
|
|
|
|
do { wprintf (L"Failure on line %d\n", __LINE__); ret = 1; } while (0)
|
|
|
|
|
#define CHK_FAIL_START \
|
|
|
|
|
chk_fail_ok = 1; \
|
stdlib: Make abort/_Exit AS-safe (BZ 26275)
The recursive lock used on abort does not synchronize with a new process
creation (either by fork-like interfaces or posix_spawn ones), nor it
is reinitialized after fork().
Also, the SIGABRT unblock before raise() shows another race condition,
where a fork or posix_spawn() call by another thread, just after the
recursive lock release and before the SIGABRT signal, might create
programs with a non-expected signal mask. With the default option
(without POSIX_SPAWN_SETSIGDEF), the process can see SIG_DFL for
SIGABRT, where it should be SIG_IGN.
To fix the AS-safe, raise() does not change the process signal mask,
and an AS-safe lock is used if a SIGABRT is installed or the process
is blocked or ignored. With the signal mask change removal,
there is no need to use a recursive loc. The lock is also taken on
both _Fork() and posix_spawn(), to avoid the spawn process to see the
abort handler as SIG_DFL.
A read-write lock is used to avoid serialize _Fork and posix_spawn
execution. Both sigaction (SIGABRT) and abort() requires to lock
as writer (since both change the disposition).
The fallback is also simplified: there is no need to use a loop of
ABORT_INSTRUCTION after _exit() (if the syscall does not terminate the
process, the system is broken).
The proposed fix changes how setjmp works on a SIGABRT handler, where
glibc does not save the signal mask. So usage like the below will now
always abort.
static volatile int chk_fail_ok;
static jmp_buf chk_fail_buf;
static void
handler (int sig)
{
if (chk_fail_ok)
{
chk_fail_ok = 0;
longjmp (chk_fail_buf, 1);
}
else
_exit (127);
}
[...]
signal (SIGABRT, handler);
[....]
chk_fail_ok = 1;
if (! setjmp (chk_fail_buf))
{
// Something that can calls abort, like a failed fortify function.
chk_fail_ok = 0;
printf ("FAIL\n");
}
Such cases will need to use sigsetjmp instead.
The _dl_start_profile calls sigaction through _profil, and to avoid
pulling abort() on loader the call is replaced with __libc_sigaction.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>
2024-10-03 18:41:10 +00:00
|
|
|
if (! sigsetjmp (chk_fail_buf, 1)) \
|
2023-12-21 18:59:19 +00:00
|
|
|
{
|
|
|
|
|
#define CHK_FAIL_END \
|
|
|
|
|
chk_fail_ok = 0; \
|
|
|
|
|
WFAIL; \
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static int
|
|
|
|
|
do_test (void)
|
|
|
|
|
{
|
|
|
|
|
set_fortify_handler (handler);
|
|
|
|
|
|
|
|
|
|
int n1, n2;
|
|
|
|
|
|
|
|
|
|
int orientation = fwide (stdout, 1);
|
|
|
|
|
if (orientation <= 0)
|
|
|
|
|
WFAIL;
|
|
|
|
|
|
|
|
|
|
/* Constant literals passed directly are always ok
|
|
|
|
|
(even with warnings about possible bugs from GCC). */
|
|
|
|
|
if (wprintf (L"%ls%n%ls%n", wstr4, &n1, wstr5, &n2) != 14
|
|
|
|
|
|| n1 != 7 || n2 != 14)
|
|
|
|
|
WFAIL;
|
|
|
|
|
|
|
|
|
|
/* In this case the format string is not known at compile time,
|
|
|
|
|
but resides in read-only memory, so is ok. */
|
|
|
|
|
if (wprintf (wstr3, wstr4, &n1, wstr5, &n2) != 14
|
|
|
|
|
|| n1 != 7 || n2 != 14)
|
|
|
|
|
WFAIL;
|
|
|
|
|
|
|
|
|
|
wcpcpy (&wbuf2[3], L"%n%ls%n");
|
|
|
|
|
/* When the format string is writable and contains %n,
|
|
|
|
|
with -D_FORTIFY_SOURCE=2 it causes __chk_fail. */
|
|
|
|
|
CHK_FAIL_START
|
|
|
|
|
if (wprintf (wbuf2, wstr4, &n1, wstr5, &n1) != 14)
|
|
|
|
|
WFAIL;
|
|
|
|
|
CHK_FAIL_END
|
|
|
|
|
|
|
|
|
|
/* But if there is no %n, even writable format string
|
|
|
|
|
should work. */
|
|
|
|
|
wbuf2[8] = L'\0';
|
|
|
|
|
if (wprintf (&wbuf2[5], wstr5) != 7)
|
|
|
|
|
WFAIL;
|
|
|
|
|
|
|
|
|
|
/* Check whether missing N$ formats are detected. */
|
|
|
|
|
CHK_FAIL_START
|
|
|
|
|
wprintf (L"%3$d\n", 1, 2, 3, 4);
|
|
|
|
|
CHK_FAIL_END
|
|
|
|
|
|
|
|
|
|
return ret;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
#include <support/test-driver.c>
|
