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/*
* Copyright (C) 2014-2018 Firejail Authors
*
* This file is part of firejail project
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "firejail.h"
#define MAX_BUF 4096
static char mbuf[MAX_BUF];
static MountData mdata;
// Convert octal escape sequence to decimal value
static int read_oct(const char *path) {
int decimal = 0;
int digit, i;
// there are always three octal digits
for (i = 1; i < 4; i++) {
digit = *(path + i);
if (digit < '0' || digit > '7') {
fprintf(stderr, "Error: cannot read /proc/self/mountinfo\n");
exit(1);
}
decimal = (decimal + digit - '0') * 8;
}
decimal /= 8;
return decimal;
}
// Restore empty spaces in pathnames extracted from /proc/self/mountinfo
static void unmangle_path(char *path) {
char *p = strchr(path, '\\');
if (p) {
if (read_oct(p) == ' ') {
*p = ' ';
int i = 3;
do {
p++;
if (*(p + i) == '\\' && read_oct(p + i) == ' ') {
*p = ' ';
i += 3;
}
else
*p = *(p + i);
} while (*p);
}
}
}
// Get info regarding the last kernel mount operation.
// The return value points to a static area, and will be overwritten by subsequent calls.
// The function does an exit(1) if anything goes wrong.
MountData *get_last_mount(void) {
// open /proc/self/mountinfo
FILE *fp = fopen("/proc/self/mountinfo", "r");
if (!fp)
goto errexit;
mbuf[0] = '\0';
while (fgets(mbuf, MAX_BUF, fp));
fclose(fp);
if (arg_debug)
printf("%s", mbuf);
// extract filesystem name, directory and filesystem type
// examples:
// 587 543 8:1 /tmp /etc rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered
// mdata.fsname: /tmp
// mdata.dir: /etc
// mdata.fstype: ext4
// 585 564 0:76 / /home/netblue/.cache rw,nosuid,nodev - tmpfs tmpfs rw
// mdata.fsname: /
// mdata.dir: /home/netblue/.cache
// mdata.fstype: tmpfs
memset(&mdata, 0, sizeof(mdata));
char *ptr = strtok(mbuf, " ");
if (!ptr)
goto errexit;
int cnt = 1;
while ((ptr = strtok(NULL, " ")) != NULL) {
cnt++;
if (cnt == 4)
mdata.fsname = ptr;
else if (cnt == 5) {
mdata.dir = ptr;
break;
}
}
ptr = strtok(NULL, "-");
if (!ptr)
goto errexit;
ptr = strtok(NULL, " ");
if (!ptr)
goto errexit;
mdata.fstype = ptr++;
if (mdata.fsname == NULL ||
mdata.dir == NULL ||
mdata.fstype == NULL)
goto errexit;
unmangle_path(mdata.fsname);
unmangle_path(mdata.dir);
if (arg_debug)
printf("fsname=%s dir=%s fstype=%s\n", mdata.fsname, mdata.dir, mdata.fstype);
return &mdata;
errexit:
fprintf(stderr, "Error: cannot read /proc/self/mountinfo\n");
exit(1);
}
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