linux/arch/um/os-Linux/mem.c
Jim Meyering 11a7ac23a2 uml: improved error handling while locating temp dir
* arch/um/os-Linux/mem.c (make_tempfile): Don't deref NULL upon failed malloc.

* arch/um/os-Linux/mem.c (make_tempfile): Handle NULL tempdir.
Don't let a long tempdir (e.g., via TMPDIR) provoke heap corruption.

[ jdike - formatting cleanups, deleted obsolete comment ]

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:43 -08:00

279 lines
5.5 KiB
C

/*
* Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/param.h>
#include "init.h"
#include "kern_constants.h"
#include "os.h"
#include "user.h"
/* Modified by which_tmpdir, which is called during early boot */
static char *default_tmpdir = "/tmp";
/*
* Modified when creating the physical memory file and when checking
* the tmp filesystem for usability, both happening during early boot.
*/
static char *tempdir = NULL;
static void __init find_tempdir(void)
{
const char *dirs[] = { "TMP", "TEMP", "TMPDIR", NULL };
int i;
char *dir = NULL;
if (tempdir != NULL)
/* We've already been called */
return;
for (i = 0; dirs[i]; i++) {
dir = getenv(dirs[i]);
if ((dir != NULL) && (*dir != '\0'))
break;
}
if ((dir == NULL) || (*dir == '\0'))
dir = default_tmpdir;
tempdir = malloc(strlen(dir) + 2);
if (tempdir == NULL) {
fprintf(stderr, "Failed to malloc tempdir, "
"errno = %d\n", errno);
return;
}
strcpy(tempdir, dir);
strcat(tempdir, "/");
}
/*
* This will return 1, with the first character in buf being the
* character following the next instance of c in the file. This will
* read the file as needed. If there's an error, -errno is returned;
* if the end of the file is reached, 0 is returned.
*/
static int next(int fd, char *buf, size_t size, char c)
{
ssize_t n;
size_t len;
char *ptr;
while ((ptr = strchr(buf, c)) == NULL) {
n = read(fd, buf, size - 1);
if (n == 0)
return 0;
else if (n < 0)
return -errno;
buf[n] = '\0';
}
ptr++;
len = strlen(ptr);
memmove(buf, ptr, len + 1);
/*
* Refill the buffer so that if there's a partial string that we care
* about, it will be completed, and we can recognize it.
*/
n = read(fd, &buf[len], size - len - 1);
if (n < 0)
return -errno;
buf[len + n] = '\0';
return 1;
}
/* which_tmpdir is called only during early boot */
static int checked_tmpdir = 0;
/*
* Look for a tmpfs mounted at /dev/shm. I couldn't find a cleaner
* way to do this than to parse /proc/mounts. statfs will return the
* same filesystem magic number and fs id for both /dev and /dev/shm
* when they are both tmpfs, so you can't tell if they are different
* filesystems. Also, there seems to be no other way of finding the
* mount point of a filesystem from within it.
*
* If a /dev/shm tmpfs entry is found, then we switch to using it.
* Otherwise, we stay with the default /tmp.
*/
static void which_tmpdir(void)
{
int fd, found;
char buf[128] = { '\0' };
if (checked_tmpdir)
return;
checked_tmpdir = 1;
printf("Checking for tmpfs mount on /dev/shm...");
fd = open("/proc/mounts", O_RDONLY);
if (fd < 0) {
printf("failed to open /proc/mounts, errno = %d\n", errno);
return;
}
while (1) {
found = next(fd, buf, ARRAY_SIZE(buf), ' ');
if (found != 1)
break;
if (!strncmp(buf, "/dev/shm", strlen("/dev/shm")))
goto found;
found = next(fd, buf, ARRAY_SIZE(buf), '\n');
if (found != 1)
break;
}
err:
if (found == 0)
printf("nothing mounted on /dev/shm\n");
else if (found < 0)
printf("read returned errno %d\n", -found);
out:
close(fd);
return;
found:
found = next(fd, buf, ARRAY_SIZE(buf), ' ');
if (found != 1)
goto err;
if (strncmp(buf, "tmpfs", strlen("tmpfs"))) {
printf("not tmpfs\n");
goto out;
}
printf("OK\n");
default_tmpdir = "/dev/shm";
goto out;
}
static int __init make_tempfile(const char *template, char **out_tempname,
int do_unlink)
{
char *tempname;
int fd;
which_tmpdir();
tempname = malloc(MAXPATHLEN);
if (tempname == NULL)
return -1;
find_tempdir();
if ((tempdir == NULL) || (strlen(tempdir) >= MAXPATHLEN))
return -1;
if (template[0] != '/')
strcpy(tempname, tempdir);
else
tempname[0] = '\0';
strncat(tempname, template, MAXPATHLEN-1-strlen(tempname));
fd = mkstemp(tempname);
if (fd < 0) {
fprintf(stderr, "open - cannot create %s: %s\n", tempname,
strerror(errno));
goto out;
}
if (do_unlink && (unlink(tempname) < 0)) {
perror("unlink");
goto out;
}
if (out_tempname) {
*out_tempname = tempname;
} else
free(tempname);
return fd;
out:
free(tempname);
return -1;
}
#define TEMPNAME_TEMPLATE "vm_file-XXXXXX"
static int __init create_tmp_file(unsigned long long len)
{
int fd, err;
char zero;
fd = make_tempfile(TEMPNAME_TEMPLATE, NULL, 1);
if (fd < 0)
exit(1);
err = fchmod(fd, 0777);
if (err < 0) {
perror("fchmod");
exit(1);
}
/*
* Seek to len - 1 because writing a character there will
* increase the file size by one byte, to the desired length.
*/
if (lseek64(fd, len - 1, SEEK_SET) < 0) {
perror("lseek64");
exit(1);
}
zero = 0;
err = write(fd, &zero, 1);
if (err != 1) {
perror("write");
exit(1);
}
return fd;
}
int __init create_mem_file(unsigned long long len)
{
int err, fd;
fd = create_tmp_file(len);
err = os_set_exec_close(fd);
if (err < 0) {
errno = -err;
perror("exec_close");
}
return fd;
}
void __init check_tmpexec(void)
{
void *addr;
int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
addr = mmap(NULL, UM_KERN_PAGE_SIZE,
PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
printf("Checking PROT_EXEC mmap in %s...",tempdir);
fflush(stdout);
if (addr == MAP_FAILED) {
err = errno;
perror("failed");
close(fd);
if (err == EPERM)
printf("%s must be not mounted noexec\n",tempdir);
exit(1);
}
printf("OK\n");
munmap(addr, UM_KERN_PAGE_SIZE);
close(fd);
}