From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933325AbbAIKyw (ORCPT ); Fri, 9 Jan 2015 05:54:52 -0500 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:44513 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757393AbbAIKc3 (ORCPT ); Fri, 9 Jan 2015 05:32:29 -0500 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Konrad Rzeszutek Wilk , Linus Torvalds , Willy Tarreau , Ingo Molnar , Jiri Slaby Subject: [PATCH 3.12 37/78] x86/tls: Validate TLS entries to protect espfix Date: Fri, 9 Jan 2015 11:31:46 +0100 Message-Id: <107436a25547580118fd93e5aaf808f6b533b639.1420799385.git.jslaby@suse.cz> X-Mailer: git-send-email 2.2.1 In-Reply-To: <72002f1f248c28d1715d10454190e209d5a20fe1.1420799385.git.jslaby@suse.cz> References: <72002f1f248c28d1715d10454190e209d5a20fe1.1420799385.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 41bdc78544b8a93a9c6814b8bbbfef966272abbe upstream. Installing a 16-bit RW data segment into the GDT defeats espfix. AFAICT this will not affect glibc, Wine, or dosemu at all. Signed-off-by: Andy Lutomirski Acked-by: H. Peter Anvin Cc: Konrad Rzeszutek Wilk Cc: Linus Torvalds Cc: Willy Tarreau Signed-off-by: Ingo Molnar Signed-off-by: Jiri Slaby --- arch/x86/kernel/tls.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/arch/x86/kernel/tls.c b/arch/x86/kernel/tls.c index f7fec09e3e3a..e7650bd71109 100644 --- a/arch/x86/kernel/tls.c +++ b/arch/x86/kernel/tls.c @@ -27,6 +27,21 @@ static int get_free_idx(void) return -ESRCH; } +static bool tls_desc_okay(const struct user_desc *info) +{ + if (LDT_empty(info)) + return true; + + /* + * espfix is required for 16-bit data segments, but espfix + * only works for LDT segments. + */ + if (!info->seg_32bit) + return false; + + return true; +} + static void set_tls_desc(struct task_struct *p, int idx, const struct user_desc *info, int n) { @@ -66,6 +81,9 @@ int do_set_thread_area(struct task_struct *p, int idx, if (copy_from_user(&info, u_info, sizeof(info))) return -EFAULT; + if (!tls_desc_okay(&info)) + return -EINVAL; + if (idx == -1) idx = info.entry_number; @@ -192,6 +210,7 @@ int regset_tls_set(struct task_struct *target, const struct user_regset *regset, { struct user_desc infobuf[GDT_ENTRY_TLS_ENTRIES]; const struct user_desc *info; + int i; if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) || (pos % sizeof(struct user_desc)) != 0 || @@ -205,6 +224,10 @@ int regset_tls_set(struct task_struct *target, const struct user_regset *regset, else info = infobuf; + for (i = 0; i < count / sizeof(struct user_desc); i++) + if (!tls_desc_okay(info + i)) + return -EINVAL; + set_tls_desc(target, GDT_ENTRY_TLS_MIN + (pos / sizeof(struct user_desc)), info, count / sizeof(struct user_desc)); -- 2.2.1