[src/trunk]: src/sys/kern Make veriexec_renamechk() more readable. Also add a...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/5b5c29f971cd
branches:  trunk
changeset: 807877:5b5c29f971cd
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Apr 25 19:10:29 2015 +0000

description:
Make veriexec_renamechk() more readable. Also add a KASSERT on vte_count.

No real functional change

diffstat:

 sys/kern/kern_veriexec.c |  100 ++++++++++++++++++++++++----------------------
 1 files changed, 53 insertions(+), 47 deletions(-)

diffs (181 lines):

diff -r cc6e1ce573eb -r 5b5c29f971cd sys/kern/kern_veriexec.c
--- a/sys/kern/kern_veriexec.c  Sat Apr 25 18:43:13 2015 +0000
+++ b/sys/kern/kern_veriexec.c  Sat Apr 25 19:10:29 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_veriexec.c,v 1.4 2015/04/25 18:43:13 maxv Exp $   */
+/*     $NetBSD: kern_veriexec.c,v 1.5 2015/04/25 19:10:29 maxv Exp $   */
 
 /*-
  * Copyright (c) 2005, 2006 Elad Efrat <elad%NetBSD.org@localhost>
@@ -29,7 +29,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_veriexec.c,v 1.4 2015/04/25 18:43:13 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_veriexec.c,v 1.5 2015/04/25 19:10:29 maxv Exp $");
 
 #include "opt_veriexec.h"
 
@@ -878,7 +878,6 @@
                return 0;
 
        rw_enter(&veriexec_op_lock, RW_READER);
-
        vfe = veriexec_get(vp);
        rw_exit(&veriexec_op_lock);
 
@@ -913,7 +912,7 @@
 veriexec_renamechk(struct lwp *l, struct vnode *fromvp, const char *fromname,
     struct vnode *tovp, const char *toname)
 {
-       struct veriexec_file_entry *vfe, *tvfe;
+       struct veriexec_file_entry *fvfe = NULL, *tvfe = NULL;
 
        if (veriexec_bypass && (veriexec_strict == VERIEXEC_LEARNING))
                return 0;
@@ -924,70 +923,73 @@
                log(LOG_ALERT, "Veriexec: Preventing rename of `%s' to "
                    "`%s', uid=%u, pid=%u: Lockdown mode.\n", fromname, toname,
                    kauth_cred_geteuid(l->l_cred), l->l_proc->p_pid);
-
                rw_exit(&veriexec_op_lock);
                return (EPERM);
        }
 
-       vfe = veriexec_get(fromvp);
-       tvfe = NULL;
+       fvfe = veriexec_get(fromvp);
        if (tovp != NULL)
                tvfe = veriexec_get(tovp);
 
-       if ((vfe != NULL) || (tvfe != NULL)) {
-               if (veriexec_strict >= VERIEXEC_IPS) {
-                       log(LOG_ALERT, "Veriexec: Preventing rename of `%s' "
-                           "to `%s', uid=%u, pid=%u: IPS mode, %s "
-                           "monitored.\n", fromname, toname,
-                           kauth_cred_geteuid(l->l_cred),
-                           l->l_proc->p_pid, (vfe != NULL && tvfe != NULL) ?
-                           "files" : "file");
+       if ((fvfe == NULL) && (tvfe == NULL)) {
+               /* None of them is monitored */
+               rw_exit(&veriexec_op_lock);
+               return 0;
+       }
 
-                       rw_exit(&veriexec_op_lock);
-                       return (EPERM);
-               }
+       if (veriexec_strict >= VERIEXEC_IPS) {
+               log(LOG_ALERT, "Veriexec: Preventing rename of `%s' "
+                   "to `%s', uid=%u, pid=%u: IPS mode, %s "
+                   "monitored.\n", fromname, toname,
+                   kauth_cred_geteuid(l->l_cred),
+                   l->l_proc->p_pid, (fvfe != NULL && tvfe != NULL) ?
+                   "files" : "file");
+               rw_exit(&veriexec_op_lock);
+               return (EPERM);
+       }
+
+       if (fvfe != NULL) {
+               /*
+                * Monitored file is renamed; filename no longer relevant.
+                */
 
                /*
-                * Monitored file is renamed; filename no longer relevant.
-                *
                 * XXX: We could keep the buffer, and when (and if) updating the
                 * XXX: filename post-rename, re-allocate it only if it's not
                 * XXX: big enough for the new filename.
                 */
-               if (vfe != NULL) {
-                       /* XXXX get write lock on vfe here? */
+
+               /* XXX: Get write lock on fvfe here? */
 
-                       VERIEXEC_RW_UPGRADE(&veriexec_op_lock);
-                       /* once we have the op lock in write mode
-                        * there should be no locks on any file
-                        * entries so we can destroy the object.
-                        */
+               VERIEXEC_RW_UPGRADE(&veriexec_op_lock);
+               /* once we have the op lock in write mode
+                * there should be no locks on any file
+                * entries so we can destroy the object.
+                */
 
-                       if (vfe->filename_len > 0)
-                               kmem_free(vfe->filename, vfe->filename_len);
+               if (fvfe->filename_len > 0)
+                       kmem_free(fvfe->filename, fvfe->filename_len);
 
-                       vfe->filename = NULL;
-                       vfe->filename_len = 0;
+               fvfe->filename = NULL;
+               fvfe->filename_len = 0;
 
-                       rw_downgrade(&veriexec_op_lock);
-               }
+               rw_downgrade(&veriexec_op_lock);
+       }
 
-               log(LOG_NOTICE, "Veriexec: %s file `%s' renamed to "
-                   "%s file `%s', uid=%u, pid=%u.\n", (vfe != NULL) ?
-                   "Monitored" : "Non-monitored", fromname, (tvfe != NULL) ?
-                   "monitored" : "non-monitored", toname,
-                   kauth_cred_geteuid(l->l_cred), l->l_proc->p_pid);
+       log(LOG_NOTICE, "Veriexec: %s file `%s' renamed to "
+           "%s file `%s', uid=%u, pid=%u.\n", (fvfe != NULL) ?
+           "Monitored" : "Non-monitored", fromname, (tvfe != NULL) ?
+           "monitored" : "non-monitored", toname,
+           kauth_cred_geteuid(l->l_cred), l->l_proc->p_pid);
 
-               rw_exit(&veriexec_op_lock);
+       rw_exit(&veriexec_op_lock);
 
+       if (tvfe != NULL) {
                /*
                 * Monitored file is overwritten. Remove the entry.
                 */
-               if (tvfe != NULL)
-                       (void)veriexec_file_delete(l, tovp);
-
-       } else
-               rw_exit(&veriexec_op_lock);
+               (void)veriexec_file_delete(l, tovp);
+       }
 
        return (0);
 }
@@ -1337,7 +1339,8 @@
 }
 
 int
-veriexec_table_delete(struct lwp *l, struct mount *mp) {
+veriexec_table_delete(struct lwp *l, struct mount *mp)
+{
        struct veriexec_table_entry *vte;
 
        vte = veriexec_table_lookup(mp);
@@ -1351,7 +1354,8 @@
 }
 
 int
-veriexec_file_delete(struct lwp *l, struct vnode *vp) {
+veriexec_file_delete(struct lwp *l, struct vnode *vp)
+{
        struct veriexec_table_entry *vte;
        int error;
 
@@ -1362,8 +1366,10 @@
        rw_enter(&veriexec_op_lock, RW_WRITER);
        error = fileassoc_clear(vp, veriexec_hook);
        rw_exit(&veriexec_op_lock);
-       if (!error)
+       if (!error) {
+               KASSERT(vte->vte_count > 0);
                vte->vte_count--;
+       }
 
        return (error);
 }