Re: kern/53850: mount(2) with MNT_UNION | MNT_UPDATE will lead to panic

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR kern/53850; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: kern/53850: mount(2) with MNT_UNION | MNT_UPDATE will lead to
 panic
Date: Thu, 10 Jan 2019 06:59:24 +0000

 On Thu, Jan 10, 2019 at 03:45:00AM +0000, n54%gmx.com@localhost wrote:
  > Updating a mounted partition to MNT_UNION will lead to a panic.
 
 Urrgh...
 
  > int
  > main(int argc, char **argv)
  > {
  >         char A[1024];
  >         mount(NULL, "/", MNT_UNION | MNT_UPDATE, A, 0);
  >         return 0;
  > }
 
 Does it also die if you do this on a mount point other than /, where
 there is actually another fs underneath?
 
 (and if you mount over /, does it then not die?)
 
 I kinda think MNT_UPDATE ought not to be allowed to turn MNT_UNION on
 and off, but if it otherwise works...
 
 -- 
 David A. Holland
 dholland%netbsd.org@localhost