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[2003:cb:c702:9000:3d6:e434:f8b4:80cf]) by smtp.gmail.com with ESMTPSA id e5-20020a05600c4e4500b003b492753826sm15354156wmq.43.2022.11.28.10.08.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Nov 2022 10:08:04 -0800 (PST) Message-ID: Date: Mon, 28 Nov 2022 19:08:03 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [PATCH v4 3/3] mm/khugepaged: Invoke MMU notifiers in shmem/file collapse paths To: Jann Horn , security@kernel.org, Andrew Morton Cc: Yang Shi , Peter Xu , John Hubbard , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20221128180252.1684965-1-jannh@google.com> <20221128180252.1684965-3-jannh@google.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20221128180252.1684965-3-jannh@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1669658888; a=rsa-sha256; cv=none; b=beUnDBXXBZiAwJA65KTm5PGkXmK1MIKJ9ARY0C6FfYevyC3Vc5eX/DavO7r/xfTEY0oLo2 IFIw0xquRIPo7Tdbj6h8d8hSmLgz3wcJjiK5y+fAqITscrL72p662cme4qHXOQMf2IPtI6 dnqH3zypJhdOfVygEz1FJ5TGgnNmG68= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=HMa9n6nZ; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf13.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1669658888; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=yI2lsl64MrMPLmal/4OD6FwI+XLJK3nNMXWiQLT1Jqw=; b=DKEkM4cipCteWp5wbipu8g5/bA0XsJpyz1cioY/juIf6o/Zfc9PazYFSUX8ElgMQWdlu0o duZ1xvQ1YDhz8zDmc/rHabYbRjCQf52T977rctbL5Ku49/11q5f31CIjKH9DKmzTcHTYyN qFsCb+T2O2JDAybYgct2T630OSQFYzg= X-Stat-Signature: eqs71uo37fdreqzakgxac6izhx4se1ta X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: DC39220015 Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=HMa9n6nZ; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf13.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com X-Rspam-User: X-HE-Tag: 1669658888-959284 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 28.11.22 19:02, Jann Horn wrote: > Any codepath that zaps page table entries must invoke MMU notifiers to > ensure that secondary MMUs (like KVM) don't keep accessing pages which > aren't mapped anymore. Secondary MMUs don't hold their own references to > pages that are mirrored over, so failing to notify them can lead to page > use-after-free. > > I'm marking this as addressing an issue introduced in commit f3f0e1d2150b > ("khugepaged: add support of collapse for tmpfs/shmem pages"), but most of > the security impact of this only came in commit 27e1f8273113 ("khugepaged: > enable collapse pmd for pte-mapped THP"), which actually omitted flushes > for the removal of present PTEs, not just for the removal of empty page > tables. > > Cc: stable@kernel.org > Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages") > Signed-off-by: Jann Horn Acked-by: David Hildenbrand -- Thanks, David / dhildenb