From: Alexander Potapenko <glider@google.com> To: "Luck, Tony" <tony.luck@intel.com> Cc: Miaohe Lin <linmiaohe@huawei.com>, Matthew Wilcox <willy@infradead.org>, Shuai Xue <xueshuai@linux.alibaba.com>, "Williams, Dan J" <dan.j.williams@intel.com>, Michael Ellerman <mpe@ellerman.id.au>, Nicholas Piggin <npiggin@gmail.com>, Christophe Leroy <christophe.leroy@csgroup.eu>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>, Naoya Horiguchi <naoya.horiguchi@nec.com>, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH v3 1/2] mm, hwpoison: Try to recover from copy-on write faults Date: Wed, 2 Nov 2022 15:27:50 +0100 [thread overview] Message-ID: <CAG_fn=WG2-k74zKv2_-jAqU+WDraJDnFZ_hM58FPgswnXs=BrA@mail.gmail.com> (raw) In-Reply-To: <SJ1PR11MB6083F63D86CDF7810F5ACDA3FC329@SJ1PR11MB6083.namprd11.prod.outlook.com> On Fri, Oct 28, 2022 at 6:14 PM Luck, Tony <tony.luck@intel.com> wrote: > > >> + vfrom = kmap_local_page(from); > >> + vto = kmap_local_page(to); > >> + ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE); > > > > In copy_user_highpage(), kmsan_unpoison_memory(page_address(to), PAGE_SIZE) is done after the copy when > > __HAVE_ARCH_COPY_USER_HIGHPAGE isn't defined. Do we need to do something similar here? But I'm not familiar > > with kmsan, so I can easy be wrong. > > It looks like that kmsan_unpoison_memory() call was added recently, after I copied > copy_user_highpage() to create copy_mc_user_highpage(). I'm not familiar with > kmsan either. Adding Alexander to this thread since they added that code. > Given that copy_mc_user_highpage() replaces one of the calls to copy_user_highpage(), it sure makes sense to call kmsan_unpoison_memory() here. KMSAN tracks the status (initialized/uninitialized) of the kernel memory. Newly allocated memory is marked uninitialized, copying memory preserves its status, and writing constants to that memory makes it initialized. Userspace memory does not have its status tracked by KMSAN, so when values are copied from the userspace, KMSAN does nothing with their status. That's why every (successful) copy_from_user event should be followed by kmsan_unpoison_memory(), which marks the corresponding kernel buffer initialized - otherwise the status of that buffer may get stale. > > Anyway, this patch looks good to me. Thanks. > > > > Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> > > Thanks for the review. > > -Tony -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
WARNING: multiple messages have this Message-ID (diff)
From: Alexander Potapenko <glider@google.com> To: "Luck, Tony" <tony.luck@intel.com> Cc: Miaohe Lin <linmiaohe@huawei.com>, Matthew Wilcox <willy@infradead.org>, Naoya Horiguchi <naoya.horiguchi@nec.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Nicholas Piggin <npiggin@gmail.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Shuai Xue <xueshuai@linux.alibaba.com>, "Williams, Dan J" <dan.j.williams@intel.com>, "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH v3 1/2] mm, hwpoison: Try to recover from copy-on write faults Date: Wed, 2 Nov 2022 15:27:50 +0100 [thread overview] Message-ID: <CAG_fn=WG2-k74zKv2_-jAqU+WDraJDnFZ_hM58FPgswnXs=BrA@mail.gmail.com> (raw) In-Reply-To: <SJ1PR11MB6083F63D86CDF7810F5ACDA3FC329@SJ1PR11MB6083.namprd11.prod.outlook.com> On Fri, Oct 28, 2022 at 6:14 PM Luck, Tony <tony.luck@intel.com> wrote: > > >> + vfrom = kmap_local_page(from); > >> + vto = kmap_local_page(to); > >> + ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE); > > > > In copy_user_highpage(), kmsan_unpoison_memory(page_address(to), PAGE_SIZE) is done after the copy when > > __HAVE_ARCH_COPY_USER_HIGHPAGE isn't defined. Do we need to do something similar here? But I'm not familiar > > with kmsan, so I can easy be wrong. > > It looks like that kmsan_unpoison_memory() call was added recently, after I copied > copy_user_highpage() to create copy_mc_user_highpage(). I'm not familiar with > kmsan either. Adding Alexander to this thread since they added that code. > Given that copy_mc_user_highpage() replaces one of the calls to copy_user_highpage(), it sure makes sense to call kmsan_unpoison_memory() here. KMSAN tracks the status (initialized/uninitialized) of the kernel memory. Newly allocated memory is marked uninitialized, copying memory preserves its status, and writing constants to that memory makes it initialized. Userspace memory does not have its status tracked by KMSAN, so when values are copied from the userspace, KMSAN does nothing with their status. That's why every (successful) copy_from_user event should be followed by kmsan_unpoison_memory(), which marks the corresponding kernel buffer initialized - otherwise the status of that buffer may get stale. > > Anyway, this patch looks good to me. Thanks. > > > > Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> > > Thanks for the review. > > -Tony -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
next prev parent reply other threads:[~2022-11-02 14:28 UTC|newest] Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-10-17 23:42 [RFC PATCH] mm, hwpoison: Recover from copy-on-write machine checks Tony Luck 2022-10-18 8:43 ` HORIGUCHI NAOYA(堀口 直也) 2022-10-18 17:52 ` Luck, Tony 2022-10-19 17:08 ` [PATCH v2] mm, hwpoison: Try to recover from copy-on write faults Tony Luck 2022-10-19 17:08 ` Tony Luck 2022-10-19 17:45 ` Dan Williams 2022-10-19 17:45 ` Dan Williams 2022-10-19 20:30 ` Luck, Tony 2022-10-19 20:30 ` Luck, Tony 2022-10-20 1:57 ` Shuai Xue 2022-10-20 1:57 ` Shuai Xue 2022-10-20 20:05 ` Tony Luck 2022-10-20 20:05 ` Tony Luck 2022-10-21 1:38 ` Miaohe Lin 2022-10-21 1:38 ` Miaohe Lin 2022-10-21 3:57 ` Luck, Tony 2022-10-21 3:57 ` Luck, Tony 2022-10-21 1:52 ` Shuai Xue 2022-10-21 1:52 ` Shuai Xue 2022-10-21 4:08 ` Tony Luck 2022-10-21 4:08 ` Tony Luck 2022-10-21 4:11 ` David Laight 2022-10-21 4:11 ` David Laight 2022-10-21 4:41 ` Luck, Tony 2022-10-21 4:41 ` Luck, Tony 2022-10-21 9:29 ` Shuai Xue 2022-10-21 9:29 ` Shuai Xue 2022-10-21 16:30 ` Luck, Tony 2022-10-21 16:30 ` Luck, Tony 2022-10-23 15:04 ` Shuai Xue 2022-10-23 15:04 ` Shuai Xue 2022-10-21 6:57 ` Shuai Xue 2022-10-21 6:57 ` Shuai Xue 2022-10-21 20:01 ` [PATCH v3 0/2] Copy-on-write poison recovery Tony Luck 2022-10-21 20:01 ` Tony Luck 2022-10-21 20:01 ` [PATCH v3 1/2] mm, hwpoison: Try to recover from copy-on write faults Tony Luck 2022-10-21 20:01 ` Tony Luck 2022-10-25 5:46 ` HORIGUCHI NAOYA(堀口 直也) 2022-10-25 5:46 ` HORIGUCHI NAOYA(堀口 直也) 2022-10-28 2:11 ` Miaohe Lin 2022-10-28 2:11 ` Miaohe Lin 2022-10-28 16:09 ` Luck, Tony 2022-10-28 16:09 ` Luck, Tony 2022-11-02 14:27 ` Alexander Potapenko [this message] 2022-11-02 14:27 ` Alexander Potapenko 2022-11-02 14:30 ` Alexander Potapenko 2022-11-02 14:30 ` Alexander Potapenko 2022-10-21 20:01 ` [PATCH v3 2/2] mm, hwpoison: When copy-on-write hits poison, take page offline Tony Luck 2022-10-21 20:01 ` Tony Luck 2022-10-28 2:28 ` Miaohe Lin 2022-10-28 2:28 ` Miaohe Lin 2022-10-28 16:13 ` Luck, Tony 2022-10-28 16:13 ` Luck, Tony 2022-10-29 1:55 ` Miaohe Lin 2022-10-29 1:55 ` Miaohe Lin 2022-10-23 15:52 ` [PATCH v3 0/2] Copy-on-write poison recovery Shuai Xue 2022-10-23 15:52 ` Shuai Xue 2022-10-26 5:19 ` Shuai Xue 2022-10-26 5:19 ` Shuai Xue 2022-10-31 20:10 ` [PATCH v4 " Tony Luck 2022-10-31 20:10 ` Tony Luck 2022-10-31 20:10 ` [PATCH v4 1/2] mm, hwpoison: Try to recover from copy-on write faults Tony Luck 2022-10-31 20:10 ` Tony Luck 2022-10-31 20:10 ` [PATCH v4 2/2] mm, hwpoison: When copy-on-write hits poison, take page offline Tony Luck 2022-10-31 20:10 ` Tony Luck 2023-05-18 21:49 ` Jane Chu 2023-05-18 22:10 ` Luck, Tony 2023-05-19 7:28 ` Greg Kroah-Hartman
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to='CAG_fn=WG2-k74zKv2_-jAqU+WDraJDnFZ_hM58FPgswnXs=BrA@mail.gmail.com' \ --to=glider@google.com \ --cc=akpm@linux-foundation.org \ --cc=christophe.leroy@csgroup.eu \ --cc=dan.j.williams@intel.com \ --cc=linmiaohe@huawei.com \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=linuxppc-dev@lists.ozlabs.org \ --cc=mpe@ellerman.id.au \ --cc=naoya.horiguchi@nec.com \ --cc=npiggin@gmail.com \ --cc=tony.luck@intel.com \ --cc=willy@infradead.org \ --cc=xueshuai@linux.alibaba.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.