selinux: add type_transition with name extension support for selinuxfs

The attached patch allows /selinux/create takes optional 4th argument
to support TYPE_TRANSITION with name extension for userspace object
managers.
If 4th argument is not supplied, it shall perform as existing kernel.
In fact, the regression test of SE-PostgreSQL works well on the patched
kernel.

Thanks,

Signed-off-by: KaiGai Kohei <kohei.kaigai@eu.nec.com>
[manually verify fuzz was not an issue, and it wasn't: eparis]
Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index ea39cb742ae5..973f5a4a6fce 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -753,11 +753,13 @@ out:
 static ssize_t sel_write_create(struct file *file, char *buf, size_t size)
 {
 	char *scon = NULL, *tcon = NULL;
+	char *namebuf = NULL, *objname = NULL;
 	u32 ssid, tsid, newsid;
 	u16 tclass;
 	ssize_t length;
 	char *newcon = NULL;
 	u32 len;
+	int nargs;
 
 	length = task_has_security(current, SECURITY__COMPUTE_CREATE);
 	if (length)
@@ -773,9 +775,17 @@ static ssize_t sel_write_create(struct file *file, char *buf, size_t size)
 	if (!tcon)
 		goto out;
 
+	length = -ENOMEM;
+	namebuf = kzalloc(size + 1, GFP_KERNEL);
+	if (!namebuf)
+		goto out;
+
 	length = -EINVAL;
-	if (sscanf(buf, "%s %s %hu", scon, tcon, &tclass) != 3)
+	nargs = sscanf(buf, "%s %s %hu %s", scon, tcon, &tclass, namebuf);
+	if (nargs < 3 || nargs > 4)
 		goto out;
+	if (nargs == 4)
+		objname = namebuf;
 
 	length = security_context_to_sid(scon, strlen(scon) + 1, &ssid);
 	if (length)
@@ -785,7 +795,8 @@ static ssize_t sel_write_create(struct file *file, char *buf, size_t size)
 	if (length)
 		goto out;
 
-	length = security_transition_sid_user(ssid, tsid, tclass, &newsid);
+	length = security_transition_sid_user(ssid, tsid, tclass,
+					      objname, &newsid);
 	if (length)
 		goto out;
 
@@ -804,6 +815,7 @@ static ssize_t sel_write_create(struct file *file, char *buf, size_t size)
 	length = len;
 out:
 	kfree(newcon);
+	kfree(namebuf);
 	kfree(tcon);
 	kfree(scon);
 	return length;