From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754450AbaFWVWY (ORCPT ); Mon, 23 Jun 2014 17:22:24 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:56794 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752722AbaFWVWW (ORCPT ); Mon, 23 Jun 2014 17:22:22 -0400 From: Andy Lutomirski Cc: "H. Peter Anvin" , Richard Weinberger , X86 ML , Eric Paris , Linux Kernel , security@kernel.org, Steven Rostedt , Borislav Petkov , =?UTF-8?q?Toralf=20F=C3=B6rster?= , Andy Lutomirski , stable@vger.kernel.org, Roland McGrath Subject: [PATCH] x86_32,entry: Do syscall exit work on badsys (CVE-2014-4508) Date: Mon, 23 Jun 2014 14:22:15 -0700 Message-Id: X-Mailer: git-send-email 1.9.3 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit To: unlisted-recipients:; (no To-header on input) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The bad syscall nr paths are their own incomprehensible route through the entry control flow. Rearrange them to work just like syscalls that return -ENOSYS. This fixes an OOPS in the audit code when fast-path auditing is enabled and sysenter gets a bad syscall nr (CVE-2014-4508). This has probably been broken since Linux 2.6.27: af0575bba0 i386 syscall audit fast-path Cc: stable@vger.kernel.org Cc: Roland McGrath Reported-by: Toralf Förster Signed-off-by: Andy Lutomirski --- I realize that the syscall audit fast path and badsys code, on 32-bit x86 no less, is possibly one of the least fun things in the kernel to review, but this is still a real security bug and should get fixed :( So I'm cc-ing a bunch of people and maybe someone will review it. arch/x86/kernel/entry_32.S | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index a2a4f46..f4258a5 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -431,9 +431,10 @@ sysenter_past_esp: jnz sysenter_audit sysenter_do_call: cmpl $(NR_syscalls), %eax - jae syscall_badsys + jae sysenter_badsys call *sys_call_table(,%eax,4) movl %eax,PT_EAX(%esp) +sysenter_after_call: LOCKDEP_SYS_EXIT DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_OFF @@ -688,7 +689,12 @@ END(syscall_fault) syscall_badsys: movl $-ENOSYS,PT_EAX(%esp) - jmp resume_userspace + jmp syscall_exit +END(syscall_badsys) + +sysenter_badsys: + movl $-ENOSYS,PT_EAX(%esp) + jmp sysenter_after_call END(syscall_badsys) CFI_ENDPROC /* -- 1.9.3