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libselinux: Mount procfs before checking /proc/filesystems

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In the case where the SELinux security module is not loaded in the
kernel and it's early enough in the boot process that /proc has not yet
been mounted, selinuxfs_exists() will incorrectly return 1, and
selinux_init_load_policy() will print a message like this to the
console:

Mount failed for selinuxfs on /sys/fs/selinux:  No such file or directory

To fix this, mount the procfs before attempting to open
/proc/filesystems, and unmount it when done if it was initially not
mounted.  This is the same thing that selinux_init_load_policy() does
when reading /proc/cmdline.

Signed-off-by: Ben Shelton <ben.shelton@ni.com>
This commit is contained in:
Ben Shelton 2015-04-15 15:56:57 -05:00 committed by Stephen Smalley
parent 16796d8dc1
commit 9df4988846
1 changed files with 17 additions and 3 deletions
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20
libselinux/src/init.c
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@ -11,6 +11,7 @@
#include <sys/vfs.h>
#include <stdint.h>
#include <limits.h>
#include <sys/mount.h>
#include "dso.h"
#include "policy.h"
@ -54,15 +55,20 @@ static int verify_selinuxmnt(const char *mnt)
int selinuxfs_exists(void)
{
int exists = 0;
int exists = 0, mnt_rc = 0;
FILE *fp = NULL;
char *buf = NULL;
size_t len;
ssize_t num;
mnt_rc = mount("proc", "/proc", "proc", 0, 0);
fp = fopen("/proc/filesystems", "r");
if (!fp)
return 1; /* Fail as if it exists */
if (!fp) {
exists = 1; /* Fail as if it exists */
goto out;
}
__fsetlocking(fp, FSETLOCKING_BYCALLER);
num = getline(&buf, &len, fp);
@ -76,6 +82,14 @@ int selinuxfs_exists(void)
free(buf);
fclose(fp);
out:
#ifndef MNT_DETACH
#define MNT_DETACH 2
#endif
if (mnt_rc == 0)
umount2("/proc", MNT_DETACH);
return exists;
}
hidden_def(selinuxfs_exists)