[src/trunk]: src/sys/compat/sys Yet another idiotic compat syscall that was d...

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

details:   https://anonhg.NetBSD.org/src/rev/d080d6696944
branches:  trunk
changeset: 973317:d080d6696944
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Jun 27 07:00:43 2020 +0000

description:
Yet another idiotic compat syscall that was developed with literally zero
test made. Simply invoking this syscall with _valid parameters_ triggers a
fatal fault, because the kernel tries to write to userland addresses.

With specially-crafted parameters it is easy to completely escalate
privileges into the kernel.

Also the size of the allocation is just obviously wrong, but it looks like
the callers are even more wrong, so not gonna fix it for now.

Reported-by: syzbot+b05096f3114b2820d81c%syzkaller.appspotmail.com@localhost

diffstat:

 sys/compat/sys/mount.h |  4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diffs (18 lines):

diff -r 4d76e0b5e2f5 -r d080d6696944 sys/compat/sys/mount.h
--- a/sys/compat/sys/mount.h    Sat Jun 27 06:57:44 2020 +0000
+++ b/sys/compat/sys/mount.h    Sat Jun 27 07:00:43 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mount.h,v 1.11 2019/10/04 01:28:02 christos Exp $      */
+/*     $NetBSD: mount.h,v 1.12 2020/06/27 07:00:43 maxv Exp $  */
 
 /*
  * Copyright (c) 1989, 1991, 1993
@@ -140,7 +140,7 @@
        struct statfs12 *s12 = STATVFSBUF_GET();
        int error;
 
-       statvfs_to_statfs12(vs, vs12);
+       statvfs_to_statfs12(vs, s12);
        error = copyout(s12, vs12, l);
        STATVFSBUF_PUT(s12);