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From 32773a99b1f0cf2b61b5f5a33359684b18aab1ed Mon Sep 17 00:00:00 2001
From: Stephen Smalley <sds@tycho.nsa.gov>
Date: Fri, 13 May 2016 11:59:47 -0400
Subject: [PATCH] Avoid mounting /proc outside of selinux_init_load_policy().
Temporarily mounting /proc within selinuxfs_exists() can cause
problems since it can be called by a libselinux constructor and
therefore may be invoked by every program linked with libselinux.
Since this was only motivated originally by a situation where
selinuxfs_exists() was called from selinux_init_load_policy()
before /proc was mounted, fix it in selinux_init_load_policy() instead.
This reverts commit 5a8d8c499b2ef80eaa7b5abe2ec68d7101e613bf
("libselinux: only mount /proc if necessary") and
commit 9df498884665d79474b79f0f30d1cd67df11bd3e
("libselinux: Mount procfs before checking /proc/filesystems").
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
---
libselinux/src/init.c | 27 +++------------------------
libselinux/src/load_policy.c | 15 ++++++++++-----
2 files changed, 13 insertions(+), 29 deletions(-)
diff --git a/libselinux/src/init.c b/libselinux/src/init.c
index 3530594..3c687a2 100644
--- libselinux/src/init.c
+++ libselinux/src/init.c
@@ -11,8 +11,6 @@
#include <sys/vfs.h>
#include <stdint.h>
#include <limits.h>
-#include <sys/mount.h>
-#include <linux/magic.h>
#include "dso.h"
#include "policy.h"
@@ -58,26 +56,15 @@ static int verify_selinuxmnt(const char *mnt)
int selinuxfs_exists(void)
{
- int exists = 0, mnt_rc = -1, rc;
- struct statfs sb;
+ int exists = 0;
FILE *fp = NULL;
char *buf = NULL;
size_t len;
ssize_t num;
- do {
- rc = statfs("/proc", &sb);
- } while (rc < 0 && errno == EINTR);
-
- if (rc == 0 && ((uint32_t)sb.f_type != (uint32_t)PROC_SUPER_MAGIC))
- mnt_rc = mount("proc", "/proc", "proc", 0, 0);
-
fp = fopen("/proc/filesystems", "r");
- if (!fp) {
- exists = 1; /* Fail as if it exists */
- goto out;
- }
-
+ if (!fp)
+ return 1; /* Fail as if it exists */
__fsetlocking(fp, FSETLOCKING_BYCALLER);
num = getline(&buf, &len, fp);
@@ -91,14 +78,6 @@ 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)
diff --git a/libselinux/src/load_policy.c b/libselinux/src/load_policy.c
index 21ee58b..4f39fc7 100644
--- libselinux/src/load_policy.c
+++ libselinux/src/load_policy.c
@@ -17,6 +17,10 @@
#include "policy.h"
#include <limits.h>
+#ifndef MNT_DETACH
+#define MNT_DETACH 2
+#endif
+
int security_load_policy(void *data, size_t len)
{
char path[PATH_MAX];
@@ -348,11 +352,6 @@ int selinux_init_load_policy(int *enforce)
fclose(cfg);
free(buf);
}
-#ifndef MNT_DETACH
-#define MNT_DETACH 2
-#endif
- if (rc == 0)
- umount2("/proc", MNT_DETACH);
/*
* Determine the final desired mode.
@@ -400,11 +399,17 @@ int selinux_init_load_policy(int *enforce)
/* Only emit this error if selinux was not disabled */
fprintf(stderr, "Mount failed for selinuxfs on %s: %s\n", SELINUXMNT, strerror(errno));
}
+
+ if (rc == 0)
+ umount2("/proc", MNT_DETACH);
goto noload;
}
set_selinuxmnt(mntpoint);
+ if (rc == 0)
+ umount2("/proc", MNT_DETACH);
+
/*
* Note: The following code depends on having selinuxfs
* already mounted and selinuxmnt set above.
--
2.7.3
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