From: Balbir Singh <bsingharora@gmail.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org,
catalin.marinas@arm.com, will@kernel.org
Cc: mark.rutland@arm.com, mhocko@suse.com, david@redhat.com,
ira.weiny@intel.com, steve.capper@arm.com,
mgorman@techsingularity.net, steven.price@arm.com,
broonie@kernel.org, cai@lca.pw, ard.biesheuvel@arm.com,
cpandya@codeaurora.org, arunks@codeaurora.org,
dan.j.williams@intel.com, Robin.Murphy@arm.com,
logang@deltatee.com, valentin.schneider@arm.com,
suzuki.poulose@arm.com, osalvador@suse.de
Subject: Re: [PATCH V7 2/3] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump
Date: Sun, 15 Sep 2019 12:35:21 +1000 [thread overview]
Message-ID: <66922798-9de7-a230-8548-1f205e79ea50@gmail.com> (raw)
In-Reply-To: <1567503958-25831-3-git-send-email-anshuman.khandual@arm.com>
On 3/9/19 7:45 pm, Anshuman Khandual wrote:
> 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>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> arch/arm64/mm/ptdump_debugfs.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
> index 064163f25592..b5eebc8c4924 100644
> --- a/arch/arm64/mm/ptdump_debugfs.c
> +++ b/arch/arm64/mm/ptdump_debugfs.c
> @@ -1,5 +1,6 @@
> // SPDX-License-Identifier: GPL-2.0
> #include <linux/debugfs.h>
> +#include <linux/memory_hotplug.h>
> #include <linux/seq_file.h>
>
> #include <asm/ptdump.h>
> @@ -7,7 +8,10 @@
> 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();
Looks sane, BTW, checking other arches they might have the same race.
Is there anything special about the arch?
Acked-by: Balbir Singh <bsingharora@gmail.com>
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next prev parent reply other threads:[~2019-09-15 2:36 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-03 9:45 [PATCH V7 0/3] arm64/mm: Enable memory hot remove Anshuman Khandual
2019-09-03 9:45 ` [PATCH V7 1/3] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory() Anshuman Khandual
2019-09-04 8:16 ` David Hildenbrand
2019-09-05 4:27 ` Anshuman Khandual
2019-09-16 1:44 ` Balbir Singh
2019-09-18 9:28 ` Anshuman Khandual
2019-09-03 9:45 ` [PATCH V7 2/3] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump Anshuman Khandual
2019-09-15 2:35 ` Balbir Singh [this message]
2019-09-18 9:12 ` Anshuman Khandual
2019-09-03 9:45 ` [PATCH V7 3/3] arm64/mm: Enable memory hot remove Anshuman Khandual
2019-09-10 16:17 ` Catalin Marinas
2019-09-11 10:31 ` David Hildenbrand
2019-09-12 4:28 ` Anshuman Khandual
2019-09-12 8:37 ` Anshuman Khandual
2019-09-12 20:15 ` Catalin Marinas
2019-09-13 5:58 ` Anshuman Khandual
2019-09-13 10:09 ` Catalin Marinas
2019-09-17 4:36 ` Anshuman Khandual
2019-09-17 15:08 ` Catalin Marinas
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