[PATCH] udev selinux fix

Here is a fix for the SELinux part of udev.

Setfscreatecon() overrides the default labeling behavior of SELinux when
creating files, so it should only be used for as short of a time as
possible, around the mknod or symlink calls.  Without this, the files in
udev_db get the wrong label because the fscreatecon is reset after the
udev_db file creation instead of before.  I'm guessing the Redhat people
missed this because they modify udev_db to be one big file instead of a
directory of small files (at least that's what I'm told).  I created
selinux_resetfscreatecon() to reset the fscreatecon asap after the
file/node is created.

Fixed a memory leak in selinux_init.  Getfscreatecon() allocates memory
for the context, and the udev code was immediately setting the pointer
(security_context_t is actually a typedef'ed char*) to NULL after the
call regardless of success/failure.  If you're wondering about the case
where there's effectively a setfscreatecon(NULL), this is ok, as its
used to tell SELinux to do the default labeling behavior.

Renamed selinux_restore() to selinux_exit() due to the changed behavior.

Fixed a couple of dbg() messages.

3 files changed, 28 insertions, 20 deletions

diff --git a/udev_add.c b/udev_add.c
index eeab1ca174..e5bd042a5c 100644
--- a/udev_add.c
+++ b/udev_add.c
@@ -83,6 +83,7 @@ create:
 
 	selinux_setfscreatecon(file, udev->kernel_name, mode);
 	retval = mknod(file, mode, devt);
+	selinux_resetfscreatecon();
 	if (retval != 0) {
 		dbg("mknod(%s, %#o, %u, %u) failed with error '%s'",
 		    file, mode, major(devt), minor(devt), strerror(errno));
@@ -196,6 +197,7 @@ static int create_node(struct udevice *udev, struct sysfs_class_device *class_de
 
 	/* create symlink(s) if requested */
 	foreach_strpart(udev->symlink, " ", pos, len) {
+		int retval;
 		char linkname[NAME_SIZE];
 		char linktarget[NAME_SIZE];
 
@@ -227,9 +229,11 @@ static int create_node(struct udevice *udev, struct sysfs_class_device *class_de
 
 		dbg("symlink(%s, %s)", linktarget, filename);
 		if (!udev->test_run) {
-			selinux_setfscreatecon(filename, udev->kernel_name, S_IFLNK);
 			unlink(filename);
-			if (symlink(linktarget, filename) != 0)
+			selinux_setfscreatecon(filename, udev->kernel_name, S_IFLNK);
+			retval = symlink(linktarget, filename);
+			selinux_resetfscreatecon();
+			if (retval != 0)
 				dbg("symlink(%s, %s) failed with error '%s'",
 				    linktarget, filename, strerror(errno));
 		}
@@ -326,7 +330,7 @@ int udev_add_device(struct udevice *udev, struct sysfs_class_device *class_dev)
 	}
 
 exit:
-	selinux_restore();
+	selinux_exit();
 
 	return retval;
 }
diff --git a/udev_selinux.c b/udev_selinux.c
index 72381f0d0d..cc6f4d7d3f 100644
--- a/udev_selinux.c
+++ b/udev_selinux.c
@@ -105,7 +105,7 @@ void selinux_setfilecon(const char *file, const char *devname, unsigned int mode
 			} 
 
 		if (setfilecon(file, scontext) < 0)
-			dbg("setfiles %s failed with error '%s'", file, strerror(errno));
+			dbg("setfilecon %s failed with error '%s'", file, strerror(errno));
 
 		freecon(scontext);
 	}
@@ -131,12 +131,20 @@ void selinux_setfscreatecon(const char *file, const char *devname, unsigned int
 			}
 
 		if (setfscreatecon(scontext) < 0)
-			dbg("setfiles %s failed with error '%s'", file, strerror(errno));
+			dbg("setfscreatecon %s failed with error '%s'", file, strerror(errno));
 
 		freecon(scontext);
 	}
 }
 
+void selinux_resetfscreatecon(void)
+{
+	if (is_selinux_running()) {
+		if (setfscreatecon(prev_scontext) < 0)
+			dbg("setfscreatecon %s failed with error '%s'", file, strerror(errno));
+	}
+}
+
 void selinux_init(void)
 {
 	/*
@@ -144,23 +152,17 @@ void selinux_init(void)
 	 * restoration creation purposes.
 	 */
 	if (is_selinux_running()) {
-		if (getfscreatecon(&prev_scontext) < 0)
+		if (getfscreatecon(&prev_scontext) < 0) {
 			dbg("getfscreatecon failed\n");
-
-		prev_scontext = NULL;
+			prev_scontext = NULL;
+		}
 	}
 }
 
-void selinux_restore(void)
+void selinux_exit(void)
 {
-	if (is_selinux_running()) {
-		/* reset the file create context to its former glory */
-		if (setfscreatecon(prev_scontext) < 0)
-			dbg("setfscreatecon failed\n");
-
-		if (prev_scontext) {
-			freecon(prev_scontext);
-			prev_scontext = NULL;
-		}
+	if (is_selinux_running() && prev_scontext) {
+		freecon(prev_scontext);
+		prev_scontext = NULL;
 	}
 }
diff --git a/udev_selinux.h b/udev_selinux.h
index 132a9a6550..d9dfeffad0 100644
--- a/udev_selinux.h
+++ b/udev_selinux.h
@@ -24,15 +24,17 @@
 
 extern void selinux_setfilecon(const char *file, const char *devname, unsigned int mode);
 extern void selinux_setfscreatecon(const char *file, const char *devname, unsigned int mode);
+extern void selinux_resetfscreatecon(void);
 extern void selinux_init(void);
-extern void selinux_restore(void);
+extern void selinux_exit(void);
 
 #else
 
 static inline void selinux_setfilecon(const char *file, const char *devname, unsigned int mode) {}
 static inline void selinux_setfscreatecon(const char *file, const char *devname, unsigned int mode) {}
+static inline void selinux_resetfscreatecon(void) {}
 static inline void selinux_init(void) {}
-static inline void selinux_restore(void) {}
+static inline void selinux_exit(void) {}
 
 #endif /* USE_SELINUX */
 #endif /* _UDEV_USE_SELINUX */