From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06AC3C4743C for ; Wed, 23 Jun 2021 12:26:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DF2E76108E for ; Wed, 23 Jun 2021 12:26:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231878AbhFWM2Y (ORCPT ); Wed, 23 Jun 2021 08:28:24 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:36778 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231394AbhFWM1L (ORCPT ); Wed, 23 Jun 2021 08:27:11 -0400 Message-Id: <20210623121457.696022863@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1624451093; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=19bkPhqsGk1+zhGXLFieLIPBnixhXt6do725A4g6wiM=; b=NgmbW6VOkcEG1H9xCi/xwlXx1E310wDVGfuUMpr6SwZth1P4soeGIkC48c5Iecrq4KtheG mj1iPpe3kCsn/WH6jfSNwBbBLIe6Uz2Pge27p35M1NTOFEdoJjOctl7sJsDLd/jlyko6Y4 YKn2VtKt4aCeNcVQ4PPO1ZTi/84s+uzuIC55xPjuRXZyeSq1G7cr1xcZGMXu5tlMwyhIxZ qw2vvgS3ERbMXbUKUSIGCRtEIPAsta+CtS5v7MnXT8xn7NkPPjeQqtB4zA/H3FgkzHoft9 hbThDrAj7l+tQSbh0BIcUqA2tbxkDzcrrKK2duAgN7UXEOI3Iu+B+rsYgohs9w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1624451093; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=19bkPhqsGk1+zhGXLFieLIPBnixhXt6do725A4g6wiM=; b=M7Q/d3p01DMVC6xehcORb+5tnZT1thMwCqViKmo226/P+t8ua3qH0eHKYaFz6CdjSWxwNR F7UI2f8NepWmzQBQ== Date: Wed, 23 Jun 2021 14:02:31 +0200 From: Thomas Gleixner To: LKML Cc: Andy Lutomirski , Dave Hansen , Fenghua Yu , Tony Luck , Yu-cheng Yu , Sebastian Andrzej Siewior , Borislav Petkov , Peter Zijlstra , Kan Liang , "Chang Seok Bae" , Megha Dey , Oliver Sang Subject: [patch V4 64/65] x86/fpu/signal: Handle #PF in the direct restore path References: <20210623120127.327154589@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-transfer-encoding: 8-bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If *RSTOR raises an exception, then the slow path is taken. That's wrong because if the reason was not #PF then going through the slow path is waste of time because that will end up with the same conclusion that the data is invalid. Now that the wrapper around *RSTOR return an negative error code, which is the negated trap number, it's possible to differentiate. If the *RSTOR raised #PF then handle it directly in the fast path and if it was some other exception, e.g. #GP, then give up and do not try the fast path. This removes the legacy frame FRSTOR code from the slow path because FRSTOR is not a ia32_fxstate frame and is therefore handled in the fast path. Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov --- V4: Made the #PF retry path a bit more readable. --- arch/x86/kernel/fpu/signal.c | 67 +++++++++++++++++++++---------------------- 1 file changed, 33 insertions(+), 34 deletions(-) --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -272,11 +272,17 @@ static int __restore_fpregs_from_user(vo } } -static int restore_fpregs_from_user(void __user *buf, u64 xrestore, bool fx_only) +/* + * Attempt to restore the FPU registers directly from user memory. + * Pagefaults are handled and any errors returned are fatal. + */ +static int restore_fpregs_from_user(void __user *buf, u64 xrestore, + bool fx_only, unsigned int size) { struct fpu *fpu = ¤t->thread.fpu; int ret; +retry: fpregs_lock(); pagefault_disable(); ret = __restore_fpregs_from_user(buf, xrestore, fx_only); @@ -293,14 +299,18 @@ static int restore_fpregs_from_user(void * invalidate the FPU register state otherwise the task * might preempt current and return to user space with * corrupted FPU registers. - * - * In case current owns the FPU registers then no further - * action is required. The fixup in the slow path will - * handle it correctly. */ if (test_thread_flag(TIF_NEED_FPU_LOAD)) __cpu_invalidate_fpregs_state(); fpregs_unlock(); + + /* Try to handle #PF, but anything else is fatal. */ + if (ret != -EFAULT) + return -EINVAL; + + ret = fault_in_pages_readable(buf, size); + if (!ret) + goto retry; return ret; } @@ -311,9 +321,7 @@ static int restore_fpregs_from_user(void * * It would be optimal to handle this with a single XRSTORS, but * this does not work because the rest of the FPU registers have - * been restored from a user buffer directly. The single XRSTORS - * happens below, when the user buffer has been copied to the - * kernel one. + * been restored from a user buffer directly. */ if (test_thread_flag(TIF_NEED_FPU_LOAD) && xfeatures_mask_supervisor()) os_xrstor(&fpu->state.xsave, xfeatures_mask_supervisor()); @@ -326,14 +334,13 @@ static int restore_fpregs_from_user(void static int __fpu_restore_sig(void __user *buf, void __user *buf_fx, bool ia32_fxstate) { - struct user_i387_ia32_struct *envp = NULL; int state_size = fpu_kernel_xstate_size; struct task_struct *tsk = current; struct fpu *fpu = &tsk->thread.fpu; struct user_i387_ia32_struct env; u64 user_xfeatures = 0; bool fx_only = false; - int ret = 0; + int ret; if (use_xsave()) { struct _fpx_sw_bytes fx_sw_user; @@ -354,21 +361,20 @@ static int __fpu_restore_sig(void __user * faults. If it does, fall back to the slow path below, going * through the kernel buffer with the enabled pagefault handler. */ - ret = restore_fpregs_from_user(buf_fx, user_xfeatures, fx_only); - if (likely(!ret)) - return 0; - } else { - /* - * For 32-bit frames with fxstate, copy the fxstate so it can - * be reconstructed later. - */ - ret = __copy_from_user(&env, buf, sizeof(env)); - if (ret) - return ret; - envp = &env; + return restore_fpregs_from_user(buf_fx, user_xfeatures, fx_only, + state_size); } /* + * Copy the legacy state because the FP portion of the FX frame has + * to be ignored for histerical raisins. The legacy state is folded + * in once the larger state has been copied. + */ + ret = __copy_from_user(&env, buf, sizeof(env)); + if (ret) + return ret; + + /* * By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is * not modified on context switch and that the xstate is considered * to be loaded again on return to userland (overriding last_cpu avoids @@ -382,8 +388,7 @@ static int __fpu_restore_sig(void __user * supervisor state is preserved. Save the full state for * simplicity. There is no point in optimizing this by only * saving the supervisor states and then shuffle them to - * the right place in memory. This is the slow path and the - * above XRSTOR failed or ia32_fxstate is true. Shrug. + * the right place in memory. It's ia32 mode. Shrug. */ if (xfeatures_mask_supervisor()) os_xsave(&fpu->state.xsave); @@ -399,7 +404,7 @@ static int __fpu_restore_sig(void __user if (ret) return ret; - sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures); + sanitize_restored_user_xstate(&fpu->state, &env, user_xfeatures); fpregs_lock(); if (unlikely(init_bv)) @@ -412,12 +417,12 @@ static int __fpu_restore_sig(void __user ret = os_xrstor_safe(&fpu->state.xsave, user_xfeatures | xfeatures_mask_supervisor()); - } else if (use_fxsr()) { + } else { ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size); if (ret) return -EFAULT; - sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures); + sanitize_restored_user_xstate(&fpu->state, &env, user_xfeatures); fpregs_lock(); if (use_xsave()) { @@ -428,14 +433,8 @@ static int __fpu_restore_sig(void __user } ret = fxrstor_safe(&fpu->state.fxsave); - } else { - ret = __copy_from_user(&fpu->state.fsave, buf_fx, state_size); - if (ret) - return ret; - - fpregs_lock(); - ret = frstor_safe(&fpu->state.fsave); } + if (!ret) fpregs_mark_activate(); else