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[209.85.220.65]) by mx.google.com with SMTPS id g4sor43894oif.125.2019.04.17.15.09.54 for (Google Transport Security); Wed, 17 Apr 2019 15:09:54 -0700 (PDT) Received-SPF: pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@intel-com.20150623.gappssmtp.com header.s=20150623 header.b=qxYyT4+3; spf=pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=dan.j.williams@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=dbqIQjFBMMXB1QiDrqfCIlgRtfAJx8u+7/Kk91bmkDU=; b=qxYyT4+3M1kES1Z9MB2Bc+EJPmMxlo39ENZvj07r/1BFoWw3Gzizgk83iGo7ofBitO eSnkTptB3wyvaPBZVZS7vu6hUmkZDvrnrzhDfmmwWJduxQ7RySCGfmddd22RIbAi/XRq yZNnS2HSE46V8eFMepOGpn0AmC65T5+0Lg+mth0CJ//ZptXecCmfAzLvskzcxg5rDy5n RDKbGUzmwqce0+oIRr9rOKmuc1zzcK0gBZxxhcdY/3T6KtbZFldw6MrHriHslysr0OkG 75uXpkOQRNGAYIuO1cgvKMm6VoxMITLmvb+25APghcgs6GjlpeWuK2Vb93ltPxYVROEM Cugw== X-Google-Smtp-Source: APXvYqynMZNwDQfqs8yDEzntG4uXIuFy3zSkRRV7QtLiDk67MpPov0CvVUxNNEfuZQx8w4f3273kBnv/f1nGDvPrj04= X-Received: by 2002:aca:e64f:: with SMTP id d76mr637171oih.105.1555538993969; Wed, 17 Apr 2019 15:09:53 -0700 (PDT) MIME-Version: 1.0 References: <155552633539.2015392.2477781120122237934.stgit@dwillia2-desk3.amr.corp.intel.com> <155552639290.2015392.17304211251966796338.stgit@dwillia2-desk3.amr.corp.intel.com> <20190417150202.b7cec444cf81ed44a150ea9d@linux-foundation.org> In-Reply-To: <20190417150202.b7cec444cf81ed44a150ea9d@linux-foundation.org> From: Dan Williams Date: Wed, 17 Apr 2019 15:09:42 -0700 Message-ID: Subject: Re: [PATCH v6 11/12] libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields To: Andrew Morton Cc: stable , Linux MM , linux-nvdimm , Linux Kernel Mailing List , Michal Hocko , David Hildenbrand Content-Type: text/plain; charset="UTF-8" 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 Wed, Apr 17, 2019 at 3:02 PM Andrew Morton wrote: > > On Wed, 17 Apr 2019 11:39:52 -0700 Dan Williams wrote: > > > At namespace creation time there is the potential for the "expected to > > be zero" fields of a 'pfn' info-block to be filled with indeterminate > > data. While the kernel buffer is zeroed on allocation it is immediately > > overwritten by nd_pfn_validate() filling it with the current contents of > > the on-media info-block location. For fields like, 'flags' and the > > 'padding' it potentially means that future implementations can not rely > > on those fields being zero. > > > > In preparation to stop using the 'start_pad' and 'end_trunc' fields for > > section alignment, arrange for fields that are not explicitly > > initialized to be guaranteed zero. Bump the minor version to indicate it > > is safe to assume the 'padding' and 'flags' are zero. Otherwise, this > > corruption is expected to benign since all other critical fields are > > explicitly initialized. > > > > Fixes: 32ab0a3f5170 ("libnvdimm, pmem: 'struct page' for pmem") > > Cc: > > Signed-off-by: Dan Williams > > Buried at the end of a 12 patch series. Should this be a standalone > patch, suitable for a prompt merge? It's not a problem unless a kernel implementation is explicitly expecting those fields to be zero-initialized. I only marked it for -stable in case some future kernel backports patch12. Otherwise it's benign on older kernels that don't have patch12 since all fields are indeed initialized.