65 lines
2.4 KiB
Diff
65 lines
2.4 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: Wed, 18 Oct 2017 19:39:35 +0200
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Subject: [PATCH] x86/cpuid: Prevent out of bound access in do_clear_cpu_cap()
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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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do_clear_cpu_cap() allocates a bitmap to keep track of disabled feature
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dependencies. That bitmap is sized NCAPINTS * BITS_PER_INIT. The possible
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'features' which can be handed in are larger than this, because after the
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capabilities the bug 'feature' bits occupy another 32bit. Not really
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obvious...
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So clearing any of the misfeature bits, as 32bit does for the F00F bug,
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accesses that bitmap out of bounds thereby corrupting the stack.
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Size the bitmap proper and add a sanity check to catch accidental out of
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bound access.
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Fixes: 0b00de857a64 ("x86/cpuid: Add generic table for CPUID dependencies")
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Reported-by: kernel test robot <xiaolong.ye@intel.com>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Cc: Andi Kleen <ak@linux.intel.com>
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Cc: Borislav Petkov <bp@alien8.de>
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Link: https://lkml.kernel.org/r/20171018022023.GA12058@yexl-desktop
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(cherry picked from commit 57b8b1a1856adaa849d02d547411a553a531022b)
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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 4b3a90bd20b35a97fd9ca6f6a71131f4417782e4)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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arch/x86/kernel/cpu/cpuid-deps.c | 10 ++++++++--
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1 file changed, 8 insertions(+), 2 deletions(-)
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diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
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index e48eb7313120..c1d49842a411 100644
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--- a/arch/x86/kernel/cpu/cpuid-deps.c
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+++ b/arch/x86/kernel/cpu/cpuid-deps.c
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@@ -75,11 +75,17 @@ static inline void clear_feature(struct cpuinfo_x86 *c, unsigned int feature)
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__clear_cpu_cap(c, feature);
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}
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+/* Take the capabilities and the BUG bits into account */
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+#define MAX_FEATURE_BITS ((NCAPINTS + NBUGINTS) * sizeof(u32) * 8)
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+
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static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
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{
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- bool changed;
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- DECLARE_BITMAP(disable, NCAPINTS * sizeof(u32) * 8);
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+ DECLARE_BITMAP(disable, MAX_FEATURE_BITS);
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const struct cpuid_dep *d;
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+ bool changed;
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+
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+ if (WARN_ON(feature >= MAX_FEATURE_BITS))
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+ return;
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clear_feature(c, feature);
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--
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2.14.2
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