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From: Anshuman Khandual <anshuman.khandual@arm.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org,
	catalin.marinas@arm.com, will.deacon@arm.com
Cc: mark.rutland@arm.com, mhocko@suse.com, ira.weiny@intel.com,
	david@redhat.com, cai@lca.pw, logang@deltatee.com,
	james.morse@arm.com, cpandya@codeaurora.org,
	arunks@codeaurora.org, dan.j.williams@intel.com,
	mgorman@techsingularity.net, osalvador@suse.de,
	ard.biesheuvel@arm.com
Subject: [PATCH V5 2/3] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump
Date: Wed, 29 May 2019 14:46:26 +0530	[thread overview]
Message-ID: <1559121387-674-3-git-send-email-anshuman.khandual@arm.com> (raw)
In-Reply-To: <1559121387-674-1-git-send-email-anshuman.khandual@arm.com>

The arm64 page table dump code can race with concurrent modification of the
kernel page tables. When a leaf entries are modified concurrently, the dump
code may log stale or inconsistent information for a VA range, but this is
otherwise not harmful.

When intermediate levels of table are freed, the dump code will continue to
use memory which has been freed and potentially reallocated for another
purpose. In such cases, the dump code may dereference bogus addresses,
leading to a number of potential problems.

Intermediate levels of table may by freed during memory hot-remove,
which will be enabled by a subsequent patch. To avoid racing with
this, take the memory hotplug lock when walking the kernel page table.

Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/arm64/mm/ptdump_debugfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
index 064163f..80171d1 100644
--- a/arch/arm64/mm/ptdump_debugfs.c
+++ b/arch/arm64/mm/ptdump_debugfs.c
@@ -7,7 +7,10 @@
 static int ptdump_show(struct seq_file *m, void *v)
 {
 	struct ptdump_info *info = m->private;
+
+	get_online_mems();
 	ptdump_walk_pgd(m, info);
+	put_online_mems();
 	return 0;
 }
 DEFINE_SHOW_ATTRIBUTE(ptdump);
-- 
2.7.4


  parent reply	other threads:[~2019-05-29  9:16 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-29  9:16 [PATCH V5 0/3] arm64/mm: Enable memory hot remove Anshuman Khandual
2019-05-29  9:16 ` [PATCH V5 1/3] mm/hotplug: Reorder arch_remove_memory() call in __remove_memory() Anshuman Khandual
2019-05-30 10:37   ` Mark Rutland
2019-06-07  2:28     ` Anshuman Khandual
2019-06-07  7:43       ` David Hildenbrand
2019-06-11 11:26         ` [PATCH V5 - Rebased] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory() Anshuman Khandual
2019-06-11 22:19           ` Andrew Morton
2019-06-12  4:02             ` Anshuman Khandual
2019-06-12  6:53               ` David Hildenbrand
2019-06-13  1:54                 ` Andrew Morton
2019-06-13  5:37                   ` Anshuman Khandual
2019-06-13  6:14                   ` David Hildenbrand
2019-05-29  9:16 ` Anshuman Khandual [this message]
2019-05-30 10:42   ` [PATCH V5 2/3] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump Mark Rutland
2019-05-29  9:16 ` [PATCH V5 3/3] arm64/mm: Enable memory hot remove Anshuman Khandual
2019-05-30 15:12   ` Mark Rutland
2019-06-11 14:43     ` Anshuman Khandual
2019-05-29 22:06 ` [PATCH V5 0/3] " Andrew Morton
2019-05-30  4:23   ` Anshuman Khandual
2019-05-30  7:23     ` David Hildenbrand

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