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[195.135.220.15]) by mx.google.com with ESMTPS id ec17si9905416ejb.327.2019.07.25.02.03.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Jul 2019 02:03:47 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4F278ACD1; Thu, 25 Jul 2019 09:03:47 +0000 (UTC) Date: Thu, 25 Jul 2019 11:03:41 +0200 From: Michal Hocko To: Toshiki Fukasawa Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "dan.j.williams@intel.com" , "adobriyan@gmail.com" , "hch@lst.de" , Naoya Horiguchi , Junichi Nomura , "stable@vger.kernel.org" Subject: Re: [PATCH 2/2] /proc/kpageflags: do not use uninitialized struct pages Message-ID: <20190725090341.GC13855@dhcp22.suse.cz> References: <20190725023100.31141-1-t-fukasawa@vx.jp.nec.com> <20190725023100.31141-3-t-fukasawa@vx.jp.nec.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190725023100.31141-3-t-fukasawa@vx.jp.nec.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Thu 25-07-19 02:31:18, Toshiki Fukasawa wrote: > A kernel panic was observed during reading /proc/kpageflags for > first few pfns allocated by pmem namespace: > > BUG: unable to handle page fault for address: fffffffffffffffe > [ 114.495280] #PF: supervisor read access in kernel mode > [ 114.495738] #PF: error_code(0x0000) - not-present page > [ 114.496203] PGD 17120e067 P4D 17120e067 PUD 171210067 PMD 0 > [ 114.496713] Oops: 0000 [#1] SMP PTI > [ 114.497037] CPU: 9 PID: 1202 Comm: page-types Not tainted 5.3.0-rc1 #1 > [ 114.497621] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.11.0-0-g63451fca13-prebuilt.qemu-project.org 04/01/2014 > [ 114.498706] RIP: 0010:stable_page_flags+0x27/0x3f0 > [ 114.499142] Code: 82 66 90 66 66 66 66 90 48 85 ff 0f 84 d1 03 00 00 41 54 55 48 89 fd 53 48 8b 57 08 48 8b 1f 48 8d 42 ff 83 e2 01 48 0f 44 c7 <48> 8b 00 f6 c4 02 0f 84 57 03 00 00 45 31 e4 48 8b 55 08 48 89 ef > [ 114.500788] RSP: 0018:ffffa5e601a0fe60 EFLAGS: 00010202 > [ 114.501373] RAX: fffffffffffffffe RBX: ffffffffffffffff RCX: 0000000000000000 > [ 114.502009] RDX: 0000000000000001 RSI: 00007ffca13a7310 RDI: ffffd07489000000 > [ 114.502637] RBP: ffffd07489000000 R08: 0000000000000001 R09: 0000000000000000 > [ 114.503270] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000240000 > [ 114.503896] R13: 0000000000080000 R14: 00007ffca13a7310 R15: ffffa5e601a0ff08 > [ 114.504530] FS: 00007f0266c7f540(0000) GS:ffff962dbbac0000(0000) knlGS:0000000000000000 > [ 114.505245] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 114.505754] CR2: fffffffffffffffe CR3: 000000023a204000 CR4: 00000000000006e0 > [ 114.506401] Call Trace: > [ 114.506660] kpageflags_read+0xb1/0x130 > [ 114.507051] proc_reg_read+0x39/0x60 > [ 114.507387] vfs_read+0x8a/0x140 > [ 114.507686] ksys_pread64+0x61/0xa0 > [ 114.508021] do_syscall_64+0x5f/0x1a0 > [ 114.508372] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 114.508844] RIP: 0033:0x7f0266ba426b > > The reason for the panic is that stable_page_flags() which parses > the page flags uses uninitialized struct pages reserved by the > ZONE_DEVICE driver. Why pmem hasn't initialized struct pages? Isn't that a bug that should be addressed rather than paper over it like this? -- Michal Hocko SUSE Labs