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Date:   Thu, 23 Sep 2021 19:19:41 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Peter Xu <peterx@redhat.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrea Arcangeli <aarcange@redhat.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Nadav Amit <nadav.amit@gmail.com>, Li Wang <liwan@redhat.com>
Subject: Re: [PATCH] mm/userfaultfd: selftests: Fix memory corruption with
 thp enabled
Message-Id: <20210923191941.da28da4400c11a3241a07acf@linux-foundation.org>
In-Reply-To: <20210923232512.210092-1-peterx@redhat.com>
References: <20210923232512.210092-1-peterx@redhat.com>
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On Thu, 23 Sep 2021 19:25:12 -0400 Peter Xu <peterx@redhat.com> wrote:

> In RHEL's gating selftests we've encountered memory corruption in the uffd
> event test even with upstream kernel:
> 
> ...
>
> 
> We can mark the Fixes tag upon 0db282ba2c12 as it's reported to only happen
> there, however the real "Fixes" IMHO should be 8ba6e8640844, as before that
> commit we'll always do explicit release_pages() before registration of uffd,
> and 8ba6e8640844 changed that logic by adding extra unmap/map and we didn't
> release the pages at the right place.  Meanwhile I don't have a solid glue
> anyway on whether posix_memalign() could always avoid triggering this bug,
> hence it's safer to attach this fix to commit 8ba6e8640844.
> 

Thanks.  I added a cc:stable to this.  I don't think we want selftests
in older kernels to be falsely reporting kernel bugs?