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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 26 Feb 2019 12:46:53 -0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x1QCkq1N52559976 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 26 Feb 2019 12:46:52 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 339AEAE045; Tue, 26 Feb 2019 12:46:52 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 64DE2AE051; Tue, 26 Feb 2019 12:46:51 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.8.84]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 26 Feb 2019 12:46:51 +0000 (GMT) Date: Tue, 26 Feb 2019 14:46:49 +0200 From: Mike Rapoport To: Sasha Levin Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Michal Hocko , Pavel Tatashin , Heiko Carstens , Martin Schwidefsky , Andrew Morton , Linus Torvalds , linux-mm@kvack.org Subject: Re: [PATCH AUTOSEL 4.20 66/72] mm, memory_hotplug: is_mem_section_removable do not pass the end of a zone References: <20190223210422.199966-1-sashal@kernel.org> <20190223210422.199966-66-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190223210422.199966-66-sashal@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19022612-0016-0000-0000-0000025B1407 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19022612-0017-0000-0000-000032B57643 Message-Id: <20190226124649.GH11981@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-26_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1031 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902260094 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 Sat, Feb 23, 2019 at 04:04:16PM -0500, Sasha Levin wrote: > From: Michal Hocko > > [ Upstream commit efad4e475c312456edb3c789d0996d12ed744c13 ] There is a fix for this fix [1]. It's commit 891cb2a72d821f930a39d5900cb7a3aa752c1d5b ("mm, memory_hotplug: fix off-by-one in is_pageblock_removable") in mainline. [1] https://lore.kernel.org/lkml/20190218181544.14616-1-mhocko@kernel.org/ > Patch series "mm, memory_hotplug: fix uninitialized pages fallouts", v2. > > Mikhail Zaslonko has posted fixes for the two bugs quite some time ago > [1]. I have pushed back on those fixes because I believed that it is > much better to plug the problem at the initialization time rather than > play whack-a-mole all over the hotplug code and find all the places > which expect the full memory section to be initialized. > > We have ended up with commit 2830bf6f05fb ("mm, memory_hotplug: > initialize struct pages for the full memory section") merged and cause a > regression [2][3]. The reason is that there might be memory layouts > when two NUMA nodes share the same memory section so the merged fix is > simply incorrect. > > In order to plug this hole we really have to be zone range aware in > those handlers. I have split up the original patch into two. One is > unchanged (patch 2) and I took a different approach for `removable' > crash. > > [1] http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com > [2] https://bugzilla.redhat.com/show_bug.cgi?id=1666948 > [3] http://lkml.kernel.org/r/20190125163938.GA20411@dhcp22.suse.cz > > This patch (of 2): > > Mikhail has reported the following VM_BUG_ON triggered when reading sysfs > removable state of a memory block: > > page:000003d08300c000 is uninitialized and poisoned > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > Call Trace: > is_mem_section_removable+0xb4/0x190 > show_mem_removable+0x9a/0xd8 > dev_attr_show+0x34/0x70 > sysfs_kf_seq_show+0xc8/0x148 > seq_read+0x204/0x480 > __vfs_read+0x32/0x178 > vfs_read+0x82/0x138 > ksys_read+0x5a/0xb0 > system_call+0xdc/0x2d8 > Last Breaking-Event-Address: > is_mem_section_removable+0xb4/0x190 > Kernel panic - not syncing: Fatal exception: panic_on_oops > > The reason is that the memory block spans the zone boundary and we are > stumbling over an unitialized struct page. Fix this by enforcing zone > range in is_mem_section_removable so that we never run away from a zone. > > Link: http://lkml.kernel.org/r/20190128144506.15603-2-mhocko@kernel.org > Signed-off-by: Michal Hocko > Reported-by: Mikhail Zaslonko > Debugged-by: Mikhail Zaslonko > Tested-by: Gerald Schaefer > Tested-by: Mikhail Gavrilov > Reviewed-by: Oscar Salvador > Cc: Pavel Tatashin > Cc: Heiko Carstens > Cc: Martin Schwidefsky > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds > Signed-off-by: Sasha Levin > --- > mm/memory_hotplug.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 21d94b5677e81..5ce0d929ff482 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1234,7 +1234,8 @@ static bool is_pageblock_removable_nolock(struct page *page) > bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) > { > struct page *page = pfn_to_page(start_pfn); > - struct page *end_page = page + nr_pages; > + unsigned long end_pfn = min(start_pfn + nr_pages, zone_end_pfn(page_zone(page))); > + struct page *end_page = pfn_to_page(end_pfn); > > /* Check the starting page of each pageblock within the range */ > for (; page < end_page; page = next_active_pageblock(page)) { > -- > 2.19.1 > -- Sincerely yours, Mike.