Date: Tue, 13 Dec 2022 15:25:27 -0700 From: Alan Somers <asomers@freebsd.org> To: Rick Macklem <rick.macklem@gmail.com> Cc: FreeBSD CURRENT <freebsd-current@freebsd.org> Subject: Re: What to do about a few lines in vfs_domount() never executed? Message-ID: <CAOtMX2hXN%2BG=uag5pfkLQukU2hZUKFax6SpqfnYdA_1zTM14Dg@mail.gmail.com> In-Reply-To: <CAM5tNy7DM__tj4CQ0L_-ugo5krmEvLJgbU-WFLs47MrRBuGaNQ@mail.gmail.com>
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If you're 100.0% percent sure that it will never be run, you can
delete it. But if you're only 99.9%, then I suggest converting it
into a KASSERT.
On Tue, Dec 13, 2022 at 3:20 PM Rick Macklem <rick.macklem@gmail.com> wrote:
>
> Hi,
>
> While working on getting mountd/nfsd to run in a vnet
> prison, I came across the following lines near the
> beginning of vfs_domount() in sys/kern/vfs_mount.c:
>
> if (fsflags & MNT_EXPORTED) {
> error = priv_check(td, PRIV_VFS_MOUNT_EXPORTED);
> if (error)
> return (error);
> }
>
> #1 - Since MNT_EXPORTED is never set in fsflags, this code never
> gets executed.
> --> I am asking what to do with the above code, since that
> changes for the patch that allows mountd to run in a vnet
> prison.
> #2 - priv_check(td, PRIV_VFS_MOUNT_EXPORTED) always returns 0
> because nothing in sys/kern/kern_priv.c checks
> PRIV_VFS_MOUNT_EXPORTED.
>
> I don't know what the original author's thinking was w.r.t. this.
> Setting exports already checks that the mount operation can be
> done by the requestor.
>
> So, what do you think should be done with the above code snippet?
> - Consider it cruft and delete it.
> - Try and figure out what PRIV_VFS_MOUNT_EXPORTED should check?
> - Leave it as is. After the patch that allows mountd to run in
> a vnet prison, MNT_EXPORTED will be set in fsflags, but the
> priv_check() call will just return 0. (A little overhead,
> but otherwise no semantics change.)
>
> rick
>
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