From patchwork Wed Nov 7 19:48:37 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 10672981 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8583817D4 for ; Wed, 7 Nov 2018 19:51:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 77BAD2CFB7 for ; Wed, 7 Nov 2018 19:51:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6BE382D014; Wed, 7 Nov 2018 19:51:32 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DB3582CFB7 for ; Wed, 7 Nov 2018 19:51:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727197AbeKHFVH (ORCPT ); Thu, 8 Nov 2018 00:21:07 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:41874 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725953AbeKHFVH (ORCPT ); Thu, 8 Nov 2018 00:21:07 -0500 Received: from localhost ([127.0.0.1] helo=bazinga.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1gKTp5-00070Q-J5; Wed, 07 Nov 2018 20:49:07 +0100 From: Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, Andy Lutomirski , Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel , Dave Hansen , Sebastian Andrzej Siewior Subject: [PATCH 02/23] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig() Date: Wed, 7 Nov 2018 20:48:37 +0100 Message-Id: <20181107194858.9380-3-bigeasy@linutronix.de> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181107194858.9380-1-bigeasy@linutronix.de> References: <20181107194858.9380-1-bigeasy@linutronix.de> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This is a preparation for the removal of the ->initialized member in the fpu struct. __fpu__restore_sig() is deactivating the FPU via fpu__drop() and then setting manually ->initialized followed by fpu__restore(). The result is that it is possible to manipulate fpu->state and the state of registers won't be saved/restore on a context switch which would overwrite state. Don't access the fpu->state while the content is read from user space and examined / sanitized. Use a temporary buffer kmalloc() buffer for the preparation of the FPU registers and once the state is considered okay, load it. Should something go wrong, return with and error and without altering the original FPU registers. The removal of "fpu__initialize()" is a nop because fpu->initialized is already set for the user task. Signed-off-by: Sebastian Andrzej Siewior --- arch/x86/include/asm/fpu/signal.h | 2 +- arch/x86/kernel/fpu/regset.c | 5 ++-- arch/x86/kernel/fpu/signal.c | 41 ++++++++++++------------------- 3 files changed, 19 insertions(+), 29 deletions(-) diff --git a/arch/x86/include/asm/fpu/signal.h b/arch/x86/include/asm/fpu/signal.h index 44bbc39a57b30..7fb516b6893a8 100644 --- a/arch/x86/include/asm/fpu/signal.h +++ b/arch/x86/include/asm/fpu/signal.h @@ -22,7 +22,7 @@ int ia32_setup_frame(int sig, struct ksignal *ksig, extern void convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk); -extern void convert_to_fxsr(struct task_struct *tsk, +extern void convert_to_fxsr(struct fxregs_state *fxsave, const struct user_i387_ia32_struct *env); unsigned long diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index bc02f5144b958..5dbc099178a88 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -269,11 +269,10 @@ convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk) memcpy(&to[i], &from[i], sizeof(to[0])); } -void convert_to_fxsr(struct task_struct *tsk, +void convert_to_fxsr(struct fxregs_state *fxsave, const struct user_i387_ia32_struct *env) { - struct fxregs_state *fxsave = &tsk->thread.fpu.state.fxsave; struct _fpreg *from = (struct _fpreg *) &env->st_space[0]; struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0]; int i; @@ -350,7 +349,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset, ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1); if (!ret) - convert_to_fxsr(target, &env); + convert_to_fxsr(&target->thread.fpu.state.fxsave, &env); /* * update the header bit in the xsave header, indicating the diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index 61a949d84dfa5..5777ee0c32fed 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -207,11 +207,11 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) } static inline void -sanitize_restored_xstate(struct task_struct *tsk, +sanitize_restored_xstate(union fpregs_state *state, struct user_i387_ia32_struct *ia32_env, u64 xfeatures, int fx_only) { - struct xregs_state *xsave = &tsk->thread.fpu.state.xsave; + struct xregs_state *xsave = &state->xsave; struct xstate_header *header = &xsave->header; if (use_xsave()) { @@ -238,7 +238,7 @@ sanitize_restored_xstate(struct task_struct *tsk, */ xsave->i387.mxcsr &= mxcsr_feature_mask; - convert_to_fxsr(tsk, ia32_env); + convert_to_fxsr(&state->fxsave, ia32_env); } } @@ -284,8 +284,6 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size) if (!access_ok(VERIFY_READ, buf, size)) return -EACCES; - fpu__initialize(fpu); - if (!static_cpu_has(X86_FEATURE_FPU)) return fpregs_soft_set(current, NULL, 0, sizeof(struct user_i387_ia32_struct), @@ -314,41 +312,34 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size) * thread's fpu state, reconstruct fxstate from the fsave * header. Validate and sanitize the copied state. */ + union fpregs_state *state; + void *tmp; struct user_i387_ia32_struct env; int err = 0; - /* - * Drop the current fpu which clears fpu->initialized. This ensures - * that any context-switch during the copy of the new state, - * avoids the intermediate state from getting restored/saved. - * Thus avoiding the new restored state from getting corrupted. - * We will be ready to restore/save the state only after - * fpu->initialized is again set. - */ - fpu__drop(fpu); + tmp = kmalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL); + if (!tmp) + return -ENOMEM; + state = PTR_ALIGN(tmp, 64); if (using_compacted_format()) { - err = copy_user_to_xstate(&fpu->state.xsave, buf_fx); + err = copy_user_to_xstate(&state->xsave, buf_fx); } else { - err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size); + err = __copy_from_user(&state->xsave, buf_fx, state_size); if (!err && state_size > offsetof(struct xregs_state, header)) - err = validate_xstate_header(&fpu->state.xsave.header); + err = validate_xstate_header(&state->xsave.header); } if (err || __copy_from_user(&env, buf, sizeof(env))) { - fpstate_init(&fpu->state); - trace_x86_fpu_init_state(fpu); err = -1; } else { - sanitize_restored_xstate(tsk, &env, xfeatures, fx_only); + sanitize_restored_xstate(state, &env, + xfeatures, fx_only); + copy_kernel_to_fpregs(state); } - fpu->initialized = 1; - preempt_disable(); - fpu__restore(fpu); - preempt_enable(); - + kfree(tmp); return err; } else { /*