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>

3 files changed, 25 insertions, 12 deletions

diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index bfc5218d5840..2cf670864147 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -112,8 +112,8 @@ void security_compute_av_user(u32 ssid, u32 tsid,
 int security_transition_sid(u32 ssid, u32 tsid, u16 tclass,
                             const struct qstr *qstr, u32 *out_sid);
 
-int security_transition_sid_user(u32 ssid, u32 tsid,
-                                 u16 tclass, u32 *out_sid);
+int security_transition_sid_user(u32 ssid, u32 tsid, u16 tclass,
+                                 const char *objname, u32 *out_sid);
 
 int security_member_sid(u32 ssid, u32 tsid,
         u16 tclass, u32 *out_sid);
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;
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 03f7a4748ee8..39d732145abe 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -1360,14 +1360,14 @@ out:
 
 static void filename_compute_type(struct policydb *p, struct context *newcontext,
                                   u32 scon, u32 tcon, u16 tclass,
-                                  const struct qstr *qstr)
+                                  const char *objname)
 {
         struct filename_trans *ft;
         for (ft = p->filename_trans; ft; ft = ft->next) {
                 if (ft->stype == scon &&
                     ft->ttype == tcon &&
                     ft->tclass == tclass &&
-                    !strcmp(ft->name, qstr->name)) {
+                    !strcmp(ft->name, objname)) {
                         newcontext->type = ft->otype;
                         return;
                 }
@@ -1378,7 +1378,7 @@ static int security_compute_sid(u32 ssid,
                                 u32 tsid,
                                 u16 orig_tclass,
                                 u32 specified,
-                                const struct qstr *qstr,
+                                const char *objname,
                                 u32 *out_sid,
                                 bool kern)
 {
@@ -1479,9 +1479,9 @@ static int security_compute_sid(u32 ssid,
         }
 
         /* if we have a qstr this is a file trans check so check those rules */
-        if (qstr)
+        if (objname)
                 filename_compute_type(&policydb, &newcontext, scontext->type,
-                                      tcontext->type, tclass, qstr);
+                                      tcontext->type, tclass, objname);
 
         /* Check for class-specific changes. */
         if (specified & AVTAB_TRANSITION) {
@@ -1539,13 +1539,14 @@ int security_transition_sid(u32 ssid, u32 tsid, u16 tclass,
                             const struct qstr *qstr, u32 *out_sid)
 {
         return security_compute_sid(ssid, tsid, tclass, AVTAB_TRANSITION,
-                                    qstr, out_sid, true);
+                                    qstr ? qstr->name : NULL, out_sid, true);
 }
 
-int security_transition_sid_user(u32 ssid, u32 tsid, u16 tclass, u32 *out_sid)
+int security_transition_sid_user(u32 ssid, u32 tsid, u16 tclass,
+                                 const char *objname, u32 *out_sid)
 {
         return security_compute_sid(ssid, tsid, tclass, AVTAB_TRANSITION,
-                                    NULL, out_sid, false);
+                                    objname, out_sid, false);
 }
 
 /**