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Thu, 10 Oct 2019 07:52:23 +0000 (UTC) Received: from [10.36.117.125] (ovpn-117-125.ams2.redhat.com [10.36.117.125]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0B6545C1B5; Thu, 10 Oct 2019 07:52:21 +0000 (UTC) Subject: Re: [PATCH v2 2/2] mm/memory-failure.c: Don't access uninitialized memmaps in memory_failure() To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Naoya Horiguchi , Andrew Morton References: <20191009142435.3975-1-david@redhat.com> <20191009142435.3975-3-david@redhat.com> <20191009144323.GH6681@dhcp22.suse.cz> <5a626821-77e9-e26b-c2ee-219670283bf0@redhat.com> <20191010073526.GC18412@dhcp22.suse.cz> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwX4EEwECACgFAljj9eoCGwMFCQlmAYAGCwkI BwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEE3eEPcA/4Na5IIP/3T/FIQMxIfNzZshIq687qgG 8UbspuE/YSUDdv7r5szYTK6KPTlqN8NAcSfheywbuYD9A4ZeSBWD3/NAVUdrCaRP2IvFyELj xoMvfJccbq45BxzgEspg/bVahNbyuBpLBVjVWwRtFCUEXkyazksSv8pdTMAs9IucChvFmmq3 jJ2vlaz9lYt/lxN246fIVceckPMiUveimngvXZw21VOAhfQ+/sofXF8JCFv2mFcBDoa7eYob s0FLpmqFaeNRHAlzMWgSsP80qx5nWWEvRLdKWi533N2vC/EyunN3HcBwVrXH4hxRBMco3jvM m8VKLKao9wKj82qSivUnkPIwsAGNPdFoPbgghCQiBjBe6A75Z2xHFrzo7t1jg7nQfIyNC7ez MZBJ59sqA9EDMEJPlLNIeJmqslXPjmMFnE7Mby/+335WJYDulsRybN+W5rLT5aMvhC6x6POK z55fMNKrMASCzBJum2Fwjf/VnuGRYkhKCqqZ8gJ3OvmR50tInDV2jZ1DQgc3i550T5JDpToh dPBxZocIhzg+MBSRDXcJmHOx/7nQm3iQ6iLuwmXsRC6f5FbFefk9EjuTKcLMvBsEx+2DEx0E UnmJ4hVg7u1PQ+2Oy+Lh/opK/BDiqlQ8Pz2jiXv5xkECvr/3Sv59hlOCZMOaiLTTjtOIU7Tq 7ut6OL64oAq+zsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCghCj/CA/lc/LMthqQ773ga uB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseBfDXHA6m4B3mUTWo13nid 0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts6TZ+IrPOwT1hfB4WNC+X 2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiuQmt3yqrmN63V9wzaPhC+ xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKBTccu2AXJXWAE1Xjh6GOC 8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvFFFyAS0Nk1q/7EChPcbRb hJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh2YmnmLRTro6eZ/qYwWkC u8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRkF3TwgucpyPtcpmQtTkWS gDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0LLH63+BrrHasfJzxKXzqg rW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4vq7oFCPsOgwARAQABwsFl BBgBAgAPBQJVy5+RAhsMBQkJZgGAAAoJEE3eEPcA/4NagOsP/jPoIBb/iXVbM+fmSHOjEshl KMwEl/m5iLj3iHnHPVLBUWrXPdS7iQijJA/VLxjnFknhaS60hkUNWexDMxVVP/6lbOrs4bDZ NEWDMktAeqJaFtxackPszlcpRVkAs6Msn9tu8hlvB517pyUgvuD7ZS9gGOMmYwFQDyytpepo YApVV00P0u3AaE0Cj/o71STqGJKZxcVhPaZ+LR+UCBZOyKfEyq+ZN311VpOJZ1IvTExf+S/5 lqnciDtbO3I4Wq0ArLX1gs1q1XlXLaVaA3yVqeC8E7kOchDNinD3hJS4OX0e1gdsx/e6COvy qNg5aL5n0Kl4fcVqM0LdIhsubVs4eiNCa5XMSYpXmVi3HAuFyg9dN+x8thSwI836FoMASwOl C7tHsTjnSGufB+D7F7ZBT61BffNBBIm1KdMxcxqLUVXpBQHHlGkbwI+3Ye+nE6HmZH7IwLwV W+Ajl7oYF+jeKaH4DZFtgLYGLtZ1LDwKPjX7VAsa4Yx7S5+EBAaZGxK510MjIx6SGrZWBrrV TEvdV00F2MnQoeXKzD7O4WFbL55hhyGgfWTHwZ457iN9SgYi1JLPqWkZB0JRXIEtjd4JEQcx +8Umfre0Xt4713VxMygW0PnQt5aSQdMD58jHFxTk092mU+yIHj5LeYgvwSgZN4airXk5yRXl SE+xAvmumFBY Organization: Red Hat GmbH Message-ID: <18383432-c74a-9ce5-a3c6-1e57d54cb629@redhat.com> Date: Thu, 10 Oct 2019 09:52:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191010073526.GC18412@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Thu, 10 Oct 2019 07:52:23 +0000 (UTC) Content-Transfer-Encoding: quoted-printable 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 10.10.19 09:35, Michal Hocko wrote: > On Thu 10-10-19 09:27:32, David Hildenbrand wrote: >> On 09.10.19 16:43, Michal Hocko wrote: >>> On Wed 09-10-19 16:24:35, David Hildenbrand wrote: >>>> We should check for pfn_to_online_page() to not access uninitialized >>>> memmaps. Reshuffle the code so we don't have to duplicate the error >>>> message. >>>> >>>> Cc: Naoya Horiguchi >>>> Cc: Andrew Morton >>>> Cc: Michal Hocko >>>> Signed-off-by: David Hildenbrand >>>> --- >>>> mm/memory-failure.c | 14 ++++++++------ >>>> 1 file changed, 8 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >>>> index 7ef849da8278..e866e6e5660b 100644 >>>> --- a/mm/memory-failure.c >>>> +++ b/mm/memory-failure.c >>>> @@ -1253,17 +1253,19 @@ int memory_failure(unsigned long pfn, int fl= ags) >>>> if (!sysctl_memory_failure_recovery) >>>> panic("Memory failure on page %lx", pfn); >>>> =20 >>>> - if (!pfn_valid(pfn)) { >>>> + p =3D pfn_to_online_page(pfn); >>>> + if (!p) { >>>> + if (pfn_valid(pfn)) { >>>> + pgmap =3D get_dev_pagemap(pfn, NULL); >>>> + if (pgmap) >>>> + return memory_failure_dev_pagemap(pfn, flags, >>>> + pgmap); >>>> + } >>>> pr_err("Memory failure: %#lx: memory outside kernel control\n", >>>> pfn); >>>> return -ENXIO; >>> >>> Don't we need that earlier at hwpoison_inject level? >>> >> >> Theoretically yes, this is another instance. But pfn_to_online_page(pf= n) >> alone would not be sufficient as discussed. We would, again, have to >> special-case ZONE_DEVICE via things like get_dev_pagemap() ... >> >> But mm/hwpoison-inject.c:hwpoison_inject() is a pure debug feature eit= her way: >> >> /* >> * Note that the below poison/unpoison interfaces do not involve >> * hardware status change, hence do not require hardware support. >> * They are mainly for testing hwpoison in software level. >> */ >> >> So it's not that bad compared to memory_failure() called from real HW = or >> drivers/base/memory.c:soft_offline_page_store()/hard_offline_page_stor= e() >=20 > Yes, this is just a toy. And yes we need to handle zone device pages > here because a) people likely want to test MCE behavior even on these > pages and b) HW can really trigger MCEs there as well. I was just > pointing that the patch is likely incomplete. >=20 I rather think this deserves a separate patch as it is a separate interface :) I do wonder why hwpoison_inject() has to perform so much extra work compared to other memory_failure() users. This smells like legacy leftovers to me, but I might be wrong. The interface is fairly old, though. Does anybody know why we need this magic? I can spot quite some duplicate checks/things getting performed. Naiive me would just make the interface perform the same as hard_offline_page_store(). But most probably I am not getting the real purpose of both different interfaces. HWPOISON_INJECT is only selected for DEBUG_KERNEL, so I would have guessed that fixing this is not urgent. BTW: mm/memory-failure.c:soft_offline_page() also looks wrong and needs fixing to make sure we access initialized memmaps. --=20 Thanks, David / dhildenb