From 35ef33d8c7a31a246e499588a28717ef0bfa2a91 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 31 Dec 2017 16:52:15 +0100 Subject: [PATCH 222/232] x86/ldt: Make LDT pgtable free conditional MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit CVE-2017-5754 Andy prefers to be paranoid about the pagetable free in the error path of write_ldt(). Make it conditional and warn whenever the installment of a secondary LDT fails. Requested-by: Andy Lutomirski Signed-off-by: Thomas Gleixner (cherry picked from commit 7f414195b0c3612acd12b4611a5fe75995cf10c7) Signed-off-by: Andy Whitcroft Signed-off-by: Kleber Sacilotto de Souza (cherry picked from commit 4e23d9d8427c9b2bd10176bd56dfcaca5e0d6b0f) Signed-off-by: Fabian Grünbichler --- arch/x86/kernel/ldt.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c index 9a35b7e541bc..51af781fac85 100644 --- a/arch/x86/kernel/ldt.c +++ b/arch/x86/kernel/ldt.c @@ -425,7 +425,8 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) * already installed then the PTE page is already * populated. Mop up a half populated page table. */ - free_ldt_pgtables(mm); + if (!WARN_ON_ONCE(old_ldt)) + free_ldt_pgtables(mm); free_ldt_struct(new_ldt); goto out_unlock; } -- 2.14.2