From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751355AbdIWKRj (ORCPT ); Sat, 23 Sep 2017 06:17:39 -0400 Received: from mail-wr0-f193.google.com ([209.85.128.193]:33408 "EHLO mail-wr0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750778AbdIWKRh (ORCPT ); Sat, 23 Sep 2017 06:17:37 -0400 X-Google-Smtp-Source: AOwi7QDaD4zi9r7eYMORlsmX7DyHWbp6F2v9JFSGeZkizj8hwxOrITTb4bEnY51AzHZEd7xmPrEHOw== Date: Sat, 23 Sep 2017 12:17:33 +0200 From: Ingo Molnar To: Eric Biggers Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, Andy Lutomirski , Dave Hansen , Dmitry Vyukov , Fenghua Yu , Kevin Hao , Oleg Nesterov , Wanpeng Li , Yu-cheng Yu , Michael Halcrow , Eric Biggers Subject: [PATCH] x86/fpu: Simplify fpu__activate_fpstate_read() Message-ID: <20170923101733.kyq2avp6om2d2s3n@gmail.com> References: <20170921185239.88398-1-ebiggers3@gmail.com> <20170922053314.wryoupq2vgrel24c@gmail.com> <20170922170724.GA103935@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170922170724.GA103935@gmail.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Eric Biggers wrote: > On Fri, Sep 22, 2017 at 07:33:14AM +0200, Ingo Molnar wrote: > > > > * Eric Biggers wrote: > > > > > From: Eric Biggers > > > > > > This series fixes the bug found by syzkaller where the ptrace syscall > > > can be used to set invalid bits in a task's FPU state. I also found > > > that an equivalent bug was reachable using the sigreturn syscall, so the > > > first patch fixes the bug in both cases. > > > > > > The other two patches start validating the other parts of the > > > xstate_header and make it so that invalid FPU states can no longer be > > > abused to leak the FPU registers of other processes. > > > > > > Changes since v2: > > > - Use an exception handler to handle invalid FPU states > > > (suggested by Andy Lutomirski) > > > - Check the size of xstate_header.reserved at build time > > > (suggested by Dave Hansen) > > > > > > Eric Biggers (3): > > > x86/fpu: don't let userspace set bogus xcomp_bv > > > x86/fpu: tighten validation of user-supplied xstate_header > > > x86/fpu: reinitialize FPU registers if restoring FPU state fails > > > > > > arch/x86/include/asm/fpu/internal.h | 51 +++++++++++-------------------------- > > > arch/x86/include/asm/fpu/xstate.h | 25 ++++++++++++++++++ > > > arch/x86/kernel/fpu/regset.c | 20 +++++++-------- > > > arch/x86/kernel/fpu/signal.c | 15 ++++++++--- > > > arch/x86/kernel/fpu/xstate.c | 27 ++++++++------------ > > > arch/x86/mm/extable.c | 24 +++++++++++++++++ > > > 6 files changed, 94 insertions(+), 68 deletions(-) > > > > Ok - could you please rebase these to to tip:master that is at: > > > > git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master > > > > In particular this has a WIP.x86/fpu branch with FPU fixes+changes queued up but > > not merged upstream (yet), which conflict with these changes. I'd like to merge > > them all together. > > > > Working on it, but there is a problem with current tip. PTRACE_GETREGSET is > causing the following warning: Yes, the warning should be harmless, and I fixed it locally earlier today - does the patch below solve it for you as well? Thanks, Ingo ============================> Subject: x86/fpu: Simplify fpu__activate_fpstate_read() From: Ingo Molnar Date: Sat Sep 23 11:41:23 CEST 2017 fpu__activate_fpstate_read() can only ever be called for a non-current, non-executing (stopped) task - so make sure this is checked via a warning and remove the current-task logic. This also fixes an incorrect (but harmless) warning triggered by of the earlier patches. Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/x86/kernel/fpu/core.c | 24 ++++++++---------------- 1 file changed, 8 insertions(+), 16 deletions(-) Index: linux/arch/x86/kernel/fpu/core.c =================================================================== --- linux.orig/arch/x86/kernel/fpu/core.c +++ linux/arch/x86/kernel/fpu/core.c @@ -256,26 +256,18 @@ EXPORT_SYMBOL_GPL(fpu__activate_curr); * * If the task has not used the FPU before then initialize its * fpstate. - * - * If the task has used the FPU before then save it. */ void fpu__activate_fpstate_read(struct fpu *fpu) { - /* - * If fpregs are active (in the current CPU), then - * copy them to the fpstate: - */ - if (fpu->fpstate_active) { - fpu__save(fpu); - } else { - if (!fpu->fpstate_active) { - fpstate_init(&fpu->state); - trace_x86_fpu_init_state(fpu); + WARN_ON_FPU(fpu == ¤t->thread.fpu); + + if (!fpu->fpstate_active) { + fpstate_init(&fpu->state); + trace_x86_fpu_init_state(fpu); - trace_x86_fpu_activate_state(fpu); - /* Safe to do for current and for stopped child tasks: */ - fpu->fpstate_active = 1; - } + trace_x86_fpu_activate_state(fpu); + /* Safe to do for current and for stopped child tasks: */ + fpu->fpstate_active = 1; } } From mboxrd@z Thu Jan 1 00:00:00 1970 Sender: Ingo Molnar Date: Sat, 23 Sep 2017 12:17:33 +0200 From: Ingo Molnar Message-ID: <20170923101733.kyq2avp6om2d2s3n@gmail.com> References: <20170921185239.88398-1-ebiggers3@gmail.com> <20170922053314.wryoupq2vgrel24c@gmail.com> <20170922170724.GA103935@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170922170724.GA103935@gmail.com> Subject: [kernel-hardening] [PATCH] x86/fpu: Simplify fpu__activate_fpstate_read() To: Eric Biggers Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, Andy Lutomirski , Dave Hansen , Dmitry Vyukov , Fenghua Yu , Kevin Hao , Oleg Nesterov , Wanpeng Li , Yu-cheng Yu , Michael Halcrow , Eric Biggers List-ID: * Eric Biggers wrote: > On Fri, Sep 22, 2017 at 07:33:14AM +0200, Ingo Molnar wrote: > > > > * Eric Biggers wrote: > > > > > From: Eric Biggers > > > > > > This series fixes the bug found by syzkaller where the ptrace syscall > > > can be used to set invalid bits in a task's FPU state. I also found > > > that an equivalent bug was reachable using the sigreturn syscall, so the > > > first patch fixes the bug in both cases. > > > > > > The other two patches start validating the other parts of the > > > xstate_header and make it so that invalid FPU states can no longer be > > > abused to leak the FPU registers of other processes. > > > > > > Changes since v2: > > > - Use an exception handler to handle invalid FPU states > > > (suggested by Andy Lutomirski) > > > - Check the size of xstate_header.reserved at build time > > > (suggested by Dave Hansen) > > > > > > Eric Biggers (3): > > > x86/fpu: don't let userspace set bogus xcomp_bv > > > x86/fpu: tighten validation of user-supplied xstate_header > > > x86/fpu: reinitialize FPU registers if restoring FPU state fails > > > > > > arch/x86/include/asm/fpu/internal.h | 51 +++++++++++-------------------------- > > > arch/x86/include/asm/fpu/xstate.h | 25 ++++++++++++++++++ > > > arch/x86/kernel/fpu/regset.c | 20 +++++++-------- > > > arch/x86/kernel/fpu/signal.c | 15 ++++++++--- > > > arch/x86/kernel/fpu/xstate.c | 27 ++++++++------------ > > > arch/x86/mm/extable.c | 24 +++++++++++++++++ > > > 6 files changed, 94 insertions(+), 68 deletions(-) > > > > Ok - could you please rebase these to to tip:master that is at: > > > > git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master > > > > In particular this has a WIP.x86/fpu branch with FPU fixes+changes queued up but > > not merged upstream (yet), which conflict with these changes. I'd like to merge > > them all together. > > > > Working on it, but there is a problem with current tip. PTRACE_GETREGSET is > causing the following warning: Yes, the warning should be harmless, and I fixed it locally earlier today - does the patch below solve it for you as well? Thanks, Ingo ============================> Subject: x86/fpu: Simplify fpu__activate_fpstate_read() From: Ingo Molnar Date: Sat Sep 23 11:41:23 CEST 2017 fpu__activate_fpstate_read() can only ever be called for a non-current, non-executing (stopped) task - so make sure this is checked via a warning and remove the current-task logic. This also fixes an incorrect (but harmless) warning triggered by of the earlier patches. Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/x86/kernel/fpu/core.c | 24 ++++++++---------------- 1 file changed, 8 insertions(+), 16 deletions(-) Index: linux/arch/x86/kernel/fpu/core.c =================================================================== --- linux.orig/arch/x86/kernel/fpu/core.c +++ linux/arch/x86/kernel/fpu/core.c @@ -256,26 +256,18 @@ EXPORT_SYMBOL_GPL(fpu__activate_curr); * * If the task has not used the FPU before then initialize its * fpstate. - * - * If the task has used the FPU before then save it. */ void fpu__activate_fpstate_read(struct fpu *fpu) { - /* - * If fpregs are active (in the current CPU), then - * copy them to the fpstate: - */ - if (fpu->fpstate_active) { - fpu__save(fpu); - } else { - if (!fpu->fpstate_active) { - fpstate_init(&fpu->state); - trace_x86_fpu_init_state(fpu); + WARN_ON_FPU(fpu == ¤t->thread.fpu); + + if (!fpu->fpstate_active) { + fpstate_init(&fpu->state); + trace_x86_fpu_init_state(fpu); - trace_x86_fpu_activate_state(fpu); - /* Safe to do for current and for stopped child tasks: */ - fpu->fpstate_active = 1; - } + trace_x86_fpu_activate_state(fpu); + /* Safe to do for current and for stopped child tasks: */ + fpu->fpstate_active = 1; } }