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@kernel.org Cc: mark.rutland@arm.com, david@redhat.com, cai@lca.pw, logang@deltatee.com, cpandya@codeaurora.org, arunks@codeaurora.org, dan.j.williams@intel.com, mgorman@techsingularity.net, osalvador@suse.de, ard.biesheuvel@arm.com, steve.capper@arm.com, broonie@kernel.org, valentin.schneider@arm.com, Robin.Murphy@arm.com, steven.price@arm.com, suzuki.poulose@arm.com, ira.weiny@intel.com Subject: [PATCH V10 1/2] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump Date: Fri, 11 Oct 2019 15:44:11 +0530 [thread overview] Message-ID: <1570788852-12402-2-git-send-email-anshuman.khandual@arm.com> (raw) In-Reply-To: <1570788852-12402-1-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> 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 064163f..b5eebc8 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(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); -- 2.7.4
WARNING: multiple messages have this Message-ID (diff)
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@kernel.org Cc: mark.rutland@arm.com, ira.weiny@intel.com, david@redhat.com, mgorman@techsingularity.net, steve.capper@arm.com, Robin.Murphy@arm.com, 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, logang@deltatee.com, valentin.schneider@arm.com, suzuki.poulose@arm.com, osalvador@suse.de Subject: [PATCH V10 1/2] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump Date: Fri, 11 Oct 2019 15:44:11 +0530 [thread overview] Message-ID: <1570788852-12402-2-git-send-email-anshuman.khandual@arm.com> (raw) In-Reply-To: <1570788852-12402-1-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> 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 064163f..b5eebc8 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(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); -- 2.7.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-10-11 10:14 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-11 10:14 [PATCH V10 0/2] arm64/mm: Enable memory hot remove Anshuman Khandual 2019-10-11 10:14 ` Anshuman Khandual 2019-10-11 10:14 ` Anshuman Khandual [this message] 2019-10-11 10:14 ` [PATCH V10 1/2] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump Anshuman Khandual 2019-10-11 10:14 ` [PATCH V10 2/2] arm64/mm: Enable memory hot remove Anshuman Khandual 2019-10-11 10:14 ` Anshuman Khandual
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