unveil pathname pool

[Alexander Bluhm]

Hi,

unveil(2) allocates 1024 bytes on the stack.  That is a lot.  Better
use namei pool like sys___realpath() does.

ok?

bluhm

Index: kern/vfs_syscalls.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/kern/vfs_syscalls.c,v
retrieving revision 1.331
diff -u -p -r1.331 vfs_syscalls.c
--- kern/vfs_syscalls.c 5 Aug 2019 15:13:43 -0000       1.331
+++ kern/vfs_syscalls.c 5 Aug 2019 16:41:50 -0000
@@ -969,7 +969,7 @@ sys_unveil(struct proc *p, void *v, regi
                syscallarg(const char *) path;
                syscallarg(const char *) permissions;
        } */ *uap = v;
-       char pathname[MAXPATHLEN];
+       char *pathname;
        struct nameidata nd;
        size_t pathlen;
        char permissions[5];
@@ -986,10 +986,13 @@ sys_unveil(struct proc *p, void *v, regi
        error = copyinstr(SCARG(uap, permissions), permissions,
            sizeof(permissions), NULL);
        if (error)
-               return(error);
-       error = copyinstr(SCARG(uap, path), pathname, sizeof(pathname), 
&pathlen);
-       if (error)
-               return(error);
+               return (error);
+       pathname = pool_get(&namei_pool, PR_WAITOK);
+       error = copyinstr(SCARG(uap, path), pathname, MAXPATHLEN, &pathlen);
+       if (error) {
+               pool_put(&namei_pool, pathname);
+               return (error);
+       }

 #ifdef KTRACE
        if (KTRPOINT(p, KTR_STRUCT))
@@ -1049,6 +1052,7 @@ sys_unveil(struct proc *p, void *v, regi
        pool_put(&namei_pool, nd.ni_cnd.cn_pnbuf);
 end:
        unveil_free_traversed_vnodes(&nd);
+       pool_put(&namei_pool, pathname);

        return (error);
 }