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Re: [PATCH] gnttab: drop bogus check from _cache_flush()
- To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Wed, 14 Oct 2026 17:24:57 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Roger Pau Monné <roger@xxxxxxxxxxxxxx>
- Delivery-date: Wed, 14 Oct 2026 16:25:23 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 14/10/2026 1:52 pm, Jan Beulich wrote:
> There's no such thing as an alive domain without ->grant_table, and system
> domains (on Arm) don't own any pages. The check should also not be left
> there "just in case", because if that check could legitimately yield
> "false", the page reference obtained would then need dropping on the
> subsequent error path (see XSA-520).
>
> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Reported-by: Yehyeong Lee <yhlee@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -3637,7 +3637,7 @@ static int _cache_flush(gnttab_cache_flu
>
> page = mfn_to_page(mfn);
> owner = page_get_owner_and_reference(page);
> - if ( !owner || !owner->grant_table )
> + if ( !owner )
> {
> rcu_unlock_domain(d);
> return -EPERM;
Do you remember that I already posted this patch (to the security team),
and you already reviewed it?
I'm afraid that your commit message is hard to follow, despite knowing
the details. I already have one prepared from 3 weeks ago which I think
is rather clearer to follow.
~Andrew
|
