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/* Testcase for BZ 30932.
Copyright (C) 2023-2026 Free Software Foundation, Inc.
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 <errno.h>
#include <setjmp.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <sys/resource.h>
#include <unistd.h>
#include <support/check.h>
#include <support/support.h>
#include <support/temp_file.h>
#include <support/xdlfcn.h>
static sigjmp_buf chk_fail_buf;
static volatile int ret;
static bool chk_fail_ok;
static void
handler (int sig)
{
if (chk_fail_ok)
{
chk_fail_ok = false;
longjmp (chk_fail_buf, 1);
}
else
_exit (127);
}
#define FORTIFY_FAIL \
do { printf ("Failure on line %d\n", __LINE__); ret = 1; } while (0)
#define CHK_FAIL_START \
chk_fail_ok = true; \
if (! sigsetjmp (chk_fail_buf, 1)) \
{
#define CHK_FAIL_END \
chk_fail_ok = false; \
FORTIFY_FAIL; \
}
static const char *str2 = "F";
static char writeable_format[10] = "%s";
static char relro_format[10] __attribute__ ((section (".data.rel.ro"))) =
"%s%n%s%n";
extern void init_writable (void);
extern int sprintf_writable (int *, int *);
extern int sprintf_relro (int *, int *);
extern int sprintf_writable_malloc (int *, int *);
#define str(__x) # __x
void (*init_writable_dlopen)(void);
int (*sprintf_writable_dlopen)(int *, int *);
int (*sprintf_rdonly_dlopen)(int *, int *);
int (*sprintf_writable_malloc_dlopen)(int *, int *);
static int
do_test (void)
{
set_fortify_handler (handler);
{
void *h = xdlopen ("tst-sprintf-fortify-rdonly-dlopen.so", RTLD_NOW);
init_writable_dlopen = xdlsym (h, str(init_writable));
sprintf_writable_dlopen = xdlsym (h, str(sprintf_writable));
sprintf_rdonly_dlopen = xdlsym (h, str(sprintf_relro));
sprintf_writable_malloc_dlopen = xdlsym (h, str(sprintf_writable_malloc));
}
struct rlimit rl;
int max_fd = 24;
if (getrlimit (RLIMIT_NOFILE, &rl) == -1)
FAIL_EXIT1 ("getrlimit (RLIMIT_NOFILE): %m");
max_fd = (rl.rlim_cur < max_fd ? rl.rlim_cur : max_fd);
rl.rlim_cur = max_fd;
if (setrlimit (RLIMIT_NOFILE, &rl) == -1)
FAIL_EXIT1 ("setrlimit (RLIMIT_NOFILE): %m");
/* Exhaust the file descriptor limit with temporary files. */
int nfiles = 0;
for (; nfiles < max_fd; nfiles++)
{
int fd = create_temp_file ("tst-sprintf-fortify-rdonly-.", NULL);
if (fd == -1)
{
if (errno != EMFILE)
FAIL_EXIT1 ("create_temp_file: %m");
break;
}
}
TEST_VERIFY_EXIT (nfiles != 0);
strcpy (writeable_format + 2, "%n%s%n");
init_writable ();
init_writable_dlopen ();
/* writeable_format is at a writable part of .bss segment, so libc should be
able to check it without resorting to procfs. */
{
char buf[128];
int n1;
int n2;
CHK_FAIL_START
sprintf (buf, writeable_format, str2, &n1, str2, &n2);
CHK_FAIL_END
}
/* Same as before, but from an library. */
{
int n1;
int n2;
CHK_FAIL_START
sprintf_writable (&n1, &n2);
CHK_FAIL_END
}
{
int n1;
int n2;
CHK_FAIL_START
sprintf_writable_dlopen (&n1, &n2);
CHK_FAIL_END
}
/* relro_format is at a readonly part of .bss segment, so '%n' in format input
should not trigger a fortify failure. */
{
char buf[128];
int n1;
int n2;
if (sprintf (buf, relro_format, str2, &n1, str2, &n2) != 2
|| n1 != 1 || n2 != 2)
FAIL_EXIT1 ("sprintf failed: %s %d %d", buf, n1, n2);
}
/* Same as before, but from an library. */
{
int n1;
int n2;
if (sprintf_relro (&n1, &n2) != 2 || n1 != 1 || n2 != 2)
FAIL_EXIT1 ("sprintf failed: %d %d", n1, n2);
}
{
int n1;
int n2;
if (sprintf_rdonly_dlopen (&n1, &n2) != 2 || n1 != 1 || n2 != 2)
FAIL_EXIT1 ("sprintf failed: %d %d", n1, n2);
}
/* However if the format string is placed on a writable memory not covered
by ELF segments, libc needs to resort to procfs. */
{
char buf[128];
int n1;
int n2;
char *buf2_malloc = xstrdup (writeable_format);
CHK_FAIL_START
sprintf (buf, buf2_malloc, str2, &n1, str2, &n2);
CHK_FAIL_END
}
/* Same as before, but from an library. */
{
int n1;
int n2;
CHK_FAIL_START
sprintf_writable_malloc (&n1, &n2);
CHK_FAIL_END
}
{
int n1;
int n2;
CHK_FAIL_START
sprintf_writable_malloc_dlopen (&n1, &n2);
CHK_FAIL_END
}
return ret;
}
#include <support/test-driver.c>
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