From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:51330 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932236AbbLGMWt (ORCPT ); Mon, 7 Dec 2015 07:22:49 -0500 Subject: Patch "x86/fpu: Fix 32-bit signal frame handling" has been added to the 4.3-stable tree To: dave.hansen@linux.intel.com, bp@alien8.de, brgerst@gmail.com, dvlasenk@redhat.com, gregkh@linuxfoundation.org, hpa@zytor.com, luto@amacapital.net, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, torvalds@linux-foundation.org Cc: , From: Date: Mon, 07 Dec 2015 00:31:36 -0800 Message-ID: <1449477096235137@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled x86/fpu: Fix 32-bit signal frame handling to the 4.3-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-fpu-fix-32-bit-signal-frame-handling.patch and it can be found in the queue-4.3 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From ab6b52947545a5355154f64f449f97af9d05845f Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Tue, 10 Nov 2015 16:23:54 -0800 Subject: x86/fpu: Fix 32-bit signal frame handling From: Dave Hansen commit ab6b52947545a5355154f64f449f97af9d05845f upstream. (This should have gone to LKML originally. Sorry for the extra noise, folks on the cc.) Background: Signal frames on x86 have two formats: 1. For 32-bit executables (whether on a real 32-bit kernel or under 32-bit emulation on a 64-bit kernel) we have a 'fpregset_t' that includes the "FSAVE" registers. 2. For 64-bit executables (on 64-bit kernels obviously), the 'fpregset_t' is smaller and does not contain the "FSAVE" state. When creating the signal frame, we have to be aware of whether we are running a 32 or 64-bit executable so we create the correct format signal frame. Problem: save_xstate_epilog() uses 'fx_sw_reserved_ia32' whenever it is called for a 32-bit executable. This is for real 32-bit and ia32 emulation. But, fpu__init_prepare_fx_sw_frame() only initializes 'fx_sw_reserved_ia32' when emulation is enabled, *NOT* for real 32-bit kernels. This leads to really wierd situations where 32-bit programs lose their extended state when returning from a signal handler. The kernel copies the uninitialized (zero) 'fx_sw_reserved_ia32' out to userspace in save_xstate_epilog(). But when returning from the signal, the kernel errors out in check_for_xstate() when it does not see FP_XSTATE_MAGIC1 present (because it was zeroed). This leads to the FPU/XSAVE state being initialized. For MPX, this leads to the most permissive state and means we silently lose bounds violations. I think this would also mean that we could lose *ANY* FPU/SSE/AVX state. I'm not sure why no one has spotted this bug. I believe this was broken by: 72a671ced66d ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels") way back in 2012. Signed-off-by: Dave Hansen Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave@sr71.net Cc: fenghua.yu@intel.com Cc: yu-cheng.yu@intel.com Link: http://lkml.kernel.org/r/20151111002354.A0799571@viggo.jf.intel.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/fpu/signal.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -385,20 +385,19 @@ fpu__alloc_mathframe(unsigned long sp, i */ void fpu__init_prepare_fx_sw_frame(void) { - int fsave_header_size = sizeof(struct fregs_state); int size = xstate_size + FP_XSTATE_MAGIC2_SIZE; - if (config_enabled(CONFIG_X86_32)) - size += fsave_header_size; - fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1; fx_sw_reserved.extended_size = size; fx_sw_reserved.xfeatures = xfeatures_mask; fx_sw_reserved.xstate_size = xstate_size; - if (config_enabled(CONFIG_IA32_EMULATION)) { + if (config_enabled(CONFIG_IA32_EMULATION) || + config_enabled(CONFIG_X86_32)) { + int fsave_header_size = sizeof(struct fregs_state); + fx_sw_reserved_ia32 = fx_sw_reserved; - fx_sw_reserved_ia32.extended_size += fsave_header_size; + fx_sw_reserved_ia32.extended_size = size + fsave_header_size; } } Patches currently in stable-queue which might be from dave.hansen@linux.intel.com are queue-4.3/x86-fpu-fix-get_xsave_addr-behavior-under-virtualization.patch queue-4.3/x86-mpx-do-proper-get_user-when-running-32-bit-binaries-on-64-bit-kernels.patch queue-4.3/x86-mpx-fix-32-bit-address-space-calculation.patch queue-4.3/x86-fpu-fix-32-bit-signal-frame-handling.patch