2018-01-06 14:13:39 +00:00
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From 35ef33d8c7a31a246e499588a28717ef0bfa2a91 Mon Sep 17 00:00:00 2001
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Sun, 31 Dec 2017 16:52:15 +0100
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2018-01-07 12:17:59 +00:00
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Subject: [PATCH 222/233] x86/ldt: Make LDT pgtable free conditional
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2018-01-06 14:13:39 +00:00
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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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Andy prefers to be paranoid about the pagetable free in the error path of
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write_ldt(). Make it conditional and warn whenever the installment of a
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secondary LDT fails.
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Requested-by: Andy Lutomirski <luto@amacapital.net>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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(cherry picked from commit 7f414195b0c3612acd12b4611a5fe75995cf10c7)
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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 4e23d9d8427c9b2bd10176bd56dfcaca5e0d6b0f)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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arch/x86/kernel/ldt.c | 3 ++-
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1 file changed, 2 insertions(+), 1 deletion(-)
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diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
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index 9a35b7e541bc..51af781fac85 100644
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--- a/arch/x86/kernel/ldt.c
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+++ b/arch/x86/kernel/ldt.c
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@@ -425,7 +425,8 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
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* already installed then the PTE page is already
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* populated. Mop up a half populated page table.
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*/
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- free_ldt_pgtables(mm);
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+ if (!WARN_ON_ONCE(old_ldt))
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+ free_ldt_pgtables(mm);
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free_ldt_struct(new_ldt);
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goto out_unlock;
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}
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--
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2.14.2
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