From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Thomas Gleixner" , torvalds@linux-foundation.org, "Andy Lutomirski" Date: Tue, 17 Feb 2015 01:46:53 +0000 Message-ID: Subject: [PATCH 3.2 124/152] x86, tls, ldt: Stop checking lm in LDT_empty In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.2.67-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit e30ab185c490e9a9381385529e0fd32f0a399495 upstream. 32-bit programs don't have an lm bit in their ABI, so they can't reliably cause LDT_empty to return true without resorting to memset. They shouldn't need to do this. This should fix a longstanding, if minor, issue in all 64-bit kernels as well as a potential regression in the TLS hardening code. Fixes: 41bdc78544b8 x86/tls: Validate TLS entries to protect espfix Signed-off-by: Andy Lutomirski Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/72a059de55e86ad5e2935c80aa91880ddf19d07c.1421954363.git.luto@amacapital.net Signed-off-by: Thomas Gleixner Signed-off-by: Ben Hutchings --- arch/x86/include/asm/desc.h | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) --- a/arch/x86/include/asm/desc.h +++ b/arch/x86/include/asm/desc.h @@ -248,7 +248,8 @@ static inline void native_load_tls(struc gdt[GDT_ENTRY_TLS_MIN + i] = t->tls_array[i]; } -#define _LDT_empty(info) \ +/* This intentionally ignores lm, since 32-bit apps don't have that field. */ +#define LDT_empty(info) \ ((info)->base_addr == 0 && \ (info)->limit == 0 && \ (info)->contents == 0 && \ @@ -258,12 +259,6 @@ static inline void native_load_tls(struc (info)->seg_not_present == 1 && \ (info)->useable == 0) -#ifdef CONFIG_X86_64 -#define LDT_empty(info) (_LDT_empty(info) && ((info)->lm == 0)) -#else -#define LDT_empty(info) (_LDT_empty(info)) -#endif - static inline void clear_LDT(void) { set_ldt(NULL, 0);