[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <4F9BBE45-22D0-4F8D-BA56-CA3459998DC4@gmail.com>
Date: Thu, 14 Sep 2023 14:57:04 -0700
From: Nadav Amit <nadav.amit@...il.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, viro@...iv.linux.org.uk,
brauner@...nel.org, shuah@...nel.org,
Andrea Arcangeli <aarcange@...hat.com>, lokeshgidra@...gle.com,
Peter Xu <peterx@...hat.com>,
David Hildenbrand <david@...hat.com>,
Hugh Dickins <hughd@...gle.com>, mhocko@...e.com,
Axel Rasmussen <axelrasmussen@...gle.com>,
Mike Rapoport <rppt@...nel.org>,
Matthew Wilcox <willy@...radead.org>, Liam.Howlett@...cle.com,
Jann Horn <jannh@...gle.com>, zhangpeng362@...wei.com,
bgeffon@...gle.com, kaleshsingh@...gle.com, ngeoffray@...gle.com,
jdduke@...gle.com, linux-mm <linux-mm@...ck.org>,
linux-fsdevel@...r.kernel.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-kselftest@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH 2/3] userfaultfd: UFFDIO_REMAP uABI
> On Sep 14, 2023, at 8:26 AM, Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> + if (!pte_same(ptep_clear_flush(src_vma, src_addr, src_pte),
> + orig_src_pte))
> + BUG_ON(1);
Just a minor detail regarding these few lines:
Besides the less-than-ideal use of BUG_ON() here, I think that this code
assumes that the PTE cannot change at this point. However, as the PTE was
still mapped at this point, I think the access and dirty bits can be set.
tl;dr: this appears to be triggerable by userspace.
[ as for the performance of this code, the lack of batching would mean
that for multithreaded applications where more than a single page is
remapped, performance would suffer ]
Powered by blists - more mailing lists