From: Peter Xu <peterx@redhat.com>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, Nadav Amit <namit@vmware.com>,
Andrea Arcangeli <aarcange@redhat.com>,
stable@vger.kernel.org
Subject: Re: [PATCH] userfaultfd: fix a race between writeprotect and exit_mmap()
Date: Wed, 22 Sep 2021 10:30:53 -0400 [thread overview]
Message-ID: <YUs+HZOf6mnI6mm2@t490s> (raw)
In-Reply-To: <20210921200247.25749-1-namit@vmware.com>
On Tue, Sep 21, 2021 at 01:02:47PM -0700, Nadav Amit wrote:
> From: Nadav Amit <namit@vmware.com>
>
> A race is possible when a process exits, its VMAs are removed
> by exit_mmap() and at the same time userfaultfd_writeprotect() is
> called.
>
> The race was detected by KASAN on a development kernel, but it appears
> to be possible on vanilla kernels as well.
>
> Use mmget_not_zero() to prevent the race as done in other userfaultfd
> operations.
>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: stable@vger.kernel.org
> Fixes: 63b2d4174c4ad ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl")
> Signed-off-by: Nadav Amit <namit@vmware.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Thanks!
--
Peter Xu
next prev parent reply other threads:[~2021-09-22 14:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-21 20:02 [PATCH] userfaultfd: fix a race between writeprotect and exit_mmap() Nadav Amit
2021-09-22 14:30 ` Peter Xu [this message]
[not found] ` <CAEemH2d++nJmTkMYzNsJ-KsfdoQ=WHSFpY=EfBZn2jqVauBGAw@mail.gmail.com>
2021-09-24 0:16 ` Peter Xu
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