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[184.145.4.219]) by smtp.gmail.com with ESMTPSA id 4sm908389qtc.40.2021.05.03.14.41.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 May 2021 14:41:17 -0700 (PDT) Date: Mon, 3 May 2021 17:41:15 -0400 From: Peter Xu To: Mike Kravetz Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Andrew Morton , Andrea Arcangeli , Axel Rasmussen Subject: Re: [PATCH 2/2] mm/hugetlb: Fix cow where page writtable in child Message-ID: References: <20210501144110.8784-1-peterx@redhat.com> <20210501144110.8784-3-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=dkH1Xngp; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf23.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=peterx@redhat.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 7B782A0002D7 X-Stat-Signature: oxes4uwjcnrsx1tpmany1akr9nrwc81e Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf23; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=170.10.133.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620078073-39868 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, May 03, 2021 at 01:53:03PM -0700, Mike Kravetz wrote: > On 5/1/21 7:41 AM, Peter Xu wrote: > > When fork() and copy hugetlb page range, we'll remember to wrprotect src pte if > > needed, however we forget about the child! Without it, the child will be able > > to write to parent's pages when mapped as PROT_READ|PROT_WRITE and MAP_PRIVATE, > > which will cause data corruption in the parent process. > > > > This issue can also be exposed by "memfd_test hugetlbfs" kselftest (if it can > > pass the F_SEAL_FUTURE_WRITE test first, though). > > > > Signed-off-by: Peter Xu > > --- > > mm/hugetlb.c | 2 ++ > > 1 file changed, 2 insertions(+) > > Reviewed-by: Mike Kravetz Thanks! > > I think we need to add, "Fixes: 4eae4efa2c29" as this is now in v5.12 I could be mistaken, but my understanding is it's broken from the most initial cow support of hugetlbfs in 2006... So if we want a fixes tag, maybe this? Fixes: 1e8f889b10d8d ("[PATCH] Hugetlb: Copy on Write support") -- Peter Xu