Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754580AbaKKLLp (ORCPT ); Tue, 11 Nov 2014 06:11:45 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:57955 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753040AbaKKLLl (ORCPT ); Tue, 11 Nov 2014 06:11:41 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Andy Lutomirski , Linus Torvalds , Luis Henriques Subject: [PATCH 3.16.y-ckt 168/170] x86_64, entry: Fix out of bounds read on sysenter Date: Tue, 11 Nov 2014 11:08:47 +0000 Message-Id: <1415704129-12709-169-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1415704129-12709-1-git-send-email-luis.henriques@canonical.com> References: <1415704129-12709-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit 653bc77af60911ead1f423e588f54fc2547c4957 upstream. Rusty noticed a Really Bad Bug (tm) in my NT fix. The entry code reads out of bounds, causing the NT fix to be unreliable. But, and this is much, much worse, if your stack is somehow just below the top of the direct map (or a hole), you read out of bounds and crash. Excerpt from the crash: [ 1.129513] RSP: 0018:ffff88001da4bf88 EFLAGS: 00010296 2b:* f7 84 24 90 00 00 00 testl $0x4000,0x90(%rsp) That read is deterministically above the top of the stack. I thought I even single-stepped through this code when I wrote it to check the offset, but I clearly screwed it up. Fixes: 8c7aa698baca ("x86_64, entry: Filter RFLAGS.NT on entry from userspace") Reported-by: Rusty Russell Signed-off-by: Andy Lutomirski Signed-off-by: Linus Torvalds Signed-off-by: Luis Henriques --- arch/x86/ia32/ia32entry.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index 711de084ab57..92a2e9333620 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -157,7 +157,7 @@ ENTRY(ia32_sysenter_target) * ourselves. To save a few cycles, we can check whether * NT was set instead of doing an unconditional popfq. */ - testl $X86_EFLAGS_NT,EFLAGS(%rsp) /* saved EFLAGS match cpu */ + testl $X86_EFLAGS_NT,EFLAGS-ARGOFFSET(%rsp) jnz sysenter_fix_flags sysenter_flags_fixed: -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/