50 lines
1.8 KiB
Diff
50 lines
1.8 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Sat, 23 Dec 2017 19:45:11 +0100
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Subject: [PATCH] x86/cpu_entry_area: Prevent wraparound in
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setup_cpu_entry_area_ptes() on 32bit
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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CVE-2017-5754
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The loop which populates the CPU entry area PMDs can wrap around on 32bit
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machines when the number of CPUs is small.
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It worked wonderful for NR_CPUS=64 for whatever reason and the moron who
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wrote that code did not bother to test it with !SMP.
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Check for the wraparound to fix it.
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Fixes: 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the fixmap")
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Reported-by: kernel test robot <fengguang.wu@intel.com>
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Signed-off-by: Thomas "Feels stupid" Gleixner <tglx@linutronix.de>
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Tested-by: Borislav Petkov <bp@alien8.de>
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(cherry picked from commit f6c4fd506cb626e4346aa81688f255e593a7c5a0)
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Signed-off-by: Andy Whitcroft <apw@canonical.com>
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Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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(cherry picked from commit 8a21158932b93ed7e72d16683085d55a3a06125e)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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arch/x86/mm/cpu_entry_area.c | 3 ++-
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1 file changed, 2 insertions(+), 1 deletion(-)
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diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
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index 21e8b595cbb1..fe814fd5e014 100644
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--- a/arch/x86/mm/cpu_entry_area.c
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+++ b/arch/x86/mm/cpu_entry_area.c
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@@ -122,7 +122,8 @@ static __init void setup_cpu_entry_area_ptes(void)
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start = CPU_ENTRY_AREA_BASE;
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end = start + CPU_ENTRY_AREA_MAP_SIZE;
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- for (; start < end; start += PMD_SIZE)
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+ /* Careful here: start + PMD_SIZE might wrap around */
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+ for (; start < end && start >= CPU_ENTRY_AREA_BASE; start += PMD_SIZE)
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populate_extra_pte(start);
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#endif
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}
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--
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2.14.2
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