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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id u123sm2746990qkh.120.2019.10.10.11.33.14 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 10 Oct 2019 11:33:14 -0700 (PDT) From: Qian Cai To: akpm@linux-foundation.org Cc: david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH] mm/page_owner: fix a crash after memory offline Date: Thu, 10 Oct 2019 14:32:46 -0400 Message-Id: <1570732366-16426-1-git-send-email-cai@lca.pw> X-Mailer: git-send-email 1.8.3.1 X-Bogosity: Ham, tests=bogofilter, spamicity=0.012291, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The linux-next series "mm/memory_hotplug: Shrink zones before removing memory" [1] seems make a crash easier to reproduce while reading /proc/pagetypeinfo after offlining a memory section. Fix it by using pfn_to_online_page() in the PFN walker. [1] https://lore.kernel.org/linux-mm/20191006085646.5768-1-david@redhat.com/ page:ffffea0021200000 is uninitialized and poisoned raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) There is not page extension available. ------------[ cut here ]------------ kernel BUG at include/linux/mm.h:1107! RIP: 0010:pagetypeinfo_showmixedcount_print+0x4fb/0x680 Call Trace: walk_zones_in_node+0x3a/0xc0 pagetypeinfo_show+0x260/0x2c0 seq_read+0x27e/0x710 proc_reg_read+0x12e/0x190 __vfs_read+0x50/0xa0 vfs_read+0xcb/0x1e0 ksys_read+0xc6/0x160 __x64_sys_read+0x43/0x50 do_syscall_64+0xcc/0xaec entry_SYSCALL_64_after_hwframe+0x49/0xbe Signed-off-by: Qian Cai --- mm/page_owner.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/mm/page_owner.c b/mm/page_owner.c index dee931184788..03a6b19b3cdd 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -296,11 +296,10 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m, pageblock_mt = get_pageblock_migratetype(page); for (; pfn < block_end_pfn; pfn++) { - if (!pfn_valid_within(pfn)) + page = pfn_to_online_page(pfn); + if (!page) continue; - page = pfn_to_page(pfn); - if (page_zone(page) != zone) continue;