From patchwork Mon Aug 29 19:49:04 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kyle Huey X-Patchwork-Id: 12958386 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B368C0502C for ; Mon, 29 Aug 2022 19:49:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229646AbiH2TtM (ORCPT ); Mon, 29 Aug 2022 15:49:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46124 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229477AbiH2TtL (ORCPT ); Mon, 29 Aug 2022 15:49:11 -0400 Received: from mail-pf1-x42d.google.com (mail-pf1-x42d.google.com [IPv6:2607:f8b0:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D9AD278236 for ; Mon, 29 Aug 2022 12:49:08 -0700 (PDT) Received: by mail-pf1-x42d.google.com with SMTP id 142so9210225pfu.10 for ; Mon, 29 Aug 2022 12:49:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kylehuey.com; s=google; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc; bh=4qLQoJQNu1CZW/0PSN7Xr+tyBQTuegEan0yqmUNKFmY=; b=Hsb3PVKaTobQF/5Yd2o6lID9UVimxOlab112ao0J57/MEhIA6ClSdj5hKqivbHv34f 8ryHQTJp/sND4giNoIkGlZJWtQwA7qqQyeL5zn+vk4NWY/m187Pn54oY/anU3HCggmTb 9ulvgXAT7Veace7NpkEzI4jqmPZm3Hb88YwiB+OpfOTlHkBjL5kr9V4qpziPxCFlQC5U QQ013DXQEjQw7alE6x44p6Dqb3y570E5ZxQ1l+okXBiLO6hW+4AGxJVtQM8Zd6UrGoCx 1jrTGJznGsQKjsbSTJ/w3lq5cPwaNRPdt6AEjw8taNq/Q+TSDdouNVX04jelTTEAJOXO E+5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc; bh=4qLQoJQNu1CZW/0PSN7Xr+tyBQTuegEan0yqmUNKFmY=; b=kpknyeNyBrJMC44ApTkBzxPiSJIYLy+l4gPcskihix4UkdVMz934bBahho82dEOOAE moQoQUW3/nuI0nxFRfwH6gAC3pUrjGcMl06A8fUbVcjyPVvjSr3FYhW1Puh4WAV0S+5W PteuRI+g9WJ8/pDNVUpVXd6VxmJpsEJIKb9LJMVUSQtyb9ytpdlshISrXasYSTW5nC2W vXNKfp4gdIUwty4Q9eKLhDE8nbEy8kL9BtTQfW41Cq8+PFqpmyO1mGpJ375k5+BNkZtI DSw2X8PNX+jMJVEh4iVDbSUkhg99NjL4O5eGBtgxnUsS6/sxeQ5g0uvUF0595XQNSSmL VJHg== X-Gm-Message-State: ACgBeo26r7CCJFvtjTIUkbulY4h2a2hNX+1D/pjjnqtyMdSMetC9qUSX cOeloSwOb6w2wQ1fuPVS43osbQ== X-Google-Smtp-Source: AA6agR4eod24tlHPUImWQFEOJWEawR5Z5C8wWAkEyI8sMY9u1C+oJdMGn3mPKqCYN0wBgInG5ma53Q== X-Received: by 2002:a63:2208:0:b0:429:9444:85be with SMTP id i8-20020a632208000000b00429944485bemr15192854pgi.236.1661802548322; Mon, 29 Aug 2022 12:49:08 -0700 (PDT) Received: from minbar.home.kylehuey.com (c-71-198-251-229.hsd1.ca.comcast.net. [71.198.251.229]) by smtp.gmail.com with ESMTPSA id v12-20020a1709029a0c00b0017294d80f25sm7872364plp.258.2022.08.29.12.49.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Aug 2022 12:49:07 -0700 (PDT) From: Kyle Huey X-Google-Original-From: Kyle Huey To: Dave Hansen , Thomas Gleixner , Borislav Petkov Cc: Ingo Molnar , x86@kernel.org, "H. Peter Anvin" , Paolo Bonzini , Andy Lutomirski , Peter Zijlstra , Sean Christopherson , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, Robert O'Callahan , David Manouchehri , Kyle Huey , Borislav Petkov , stable@vger.kernel.org Subject: [PATCH v6 1/2] x86/fpu: Allow PKRU to be (once again) written by ptrace. Date: Mon, 29 Aug 2022 12:49:04 -0700 Message-Id: <20220829194905.81713-1-khuey@kylehuey.com> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Kyle Huey When management of the PKRU register was moved away from XSTATE, emulation of PKRU's existence in XSTATE was added for reading PKRU through ptrace, but not for writing PKRU through ptrace. This can be seen by running gdb and executing `p $pkru`, `set $pkru = 42`, and `p $pkru`. On affected kernels (5.14+) the write to the PKRU register (which gdb performs through ptrace) is ignored. There are three APIs that write PKRU: sigreturn, PTRACE_SETREGSET with NT_X86_XSTATE, and KVM_SET_XSAVE. sigreturn still uses XRSTOR to write to PKRU. KVM_SET_XSAVE has its own special handling to make PKRU writes take effect (in fpu_copy_uabi_to_guest_fpstate). Push that down into copy_uabi_to_xstate and have PTRACE_SETREGSET with NT_X86_XSTATE pass in a pointer to the appropriate PKRU slot. copy_sigframe_from_user_to_xstate depends on copy_uabi_to_xstate populating the PKRU field in the task's XSTATE so that __fpu_restore_sig can do a XRSTOR from it, so continue doing that. This also adds code to initialize the PKRU value to the hardware init value (namely 0) if the PKRU bit is not set in the XSTATE header provided to ptrace, to match XRSTOR. Fixes: e84ba47e313d ("x86/fpu: Hook up PKRU into ptrace()") Signed-off-by: Kyle Huey Cc: Dave Hansen Cc: Thomas Gleixner Cc: Borislav Petkov Cc: stable@vger.kernel.org # 5.14+ --- arch/x86/kernel/fpu/core.c | 20 +++++++++----------- arch/x86/kernel/fpu/regset.c | 2 +- arch/x86/kernel/fpu/signal.c | 2 +- arch/x86/kernel/fpu/xstate.c | 25 ++++++++++++++++++++----- arch/x86/kernel/fpu/xstate.h | 4 ++-- 5 files changed, 33 insertions(+), 20 deletions(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 3b28c5b25e12..c273669e8a00 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -391,8 +391,6 @@ int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, { struct fpstate *kstate = gfpu->fpstate; const union fpregs_state *ustate = buf; - struct pkru_state *xpkru; - int ret; if (!cpu_feature_enabled(X86_FEATURE_XSAVE)) { if (ustate->xsave.header.xfeatures & ~XFEATURE_MASK_FPSSE) @@ -406,16 +404,16 @@ int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, if (ustate->xsave.header.xfeatures & ~xcr0) return -EINVAL; - ret = copy_uabi_from_kernel_to_xstate(kstate, ustate); - if (ret) - return ret; + /* + * Nullify @vpkru to preserve its current value if PKRU's bit isn't set + * in the header. KVM's odd ABI is to leave PKRU untouched in this + * case (all other components are eventually re-initialized). + * (Not clear that this is actually necessary for compat). + */ + if (!(ustate->xsave.header.xfeatures & XFEATURE_MASK_PKRU)) + vpkru = NULL; - /* Retrieve PKRU if not in init state */ - if (kstate->regs.xsave.header.xfeatures & XFEATURE_MASK_PKRU) { - xpkru = get_xsave_addr(&kstate->regs.xsave, XFEATURE_PKRU); - *vpkru = xpkru->pkru; - } - return 0; + return copy_uabi_from_kernel_to_xstate(kstate, ustate, vpkru); } EXPORT_SYMBOL_GPL(fpu_copy_uabi_to_guest_fpstate); #endif /* CONFIG_KVM */ diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index 75ffaef8c299..6d056b68f4ed 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -167,7 +167,7 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset, } fpu_force_restore(fpu); - ret = copy_uabi_from_kernel_to_xstate(fpu->fpstate, kbuf ?: tmpbuf); + ret = copy_uabi_from_kernel_to_xstate(fpu->fpstate, kbuf ?: tmpbuf, &target->thread.pkru); out: vfree(tmpbuf); diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index 91d4b6de58ab..558076dbde5b 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -396,7 +396,7 @@ static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx, fpregs = &fpu->fpstate->regs; if (use_xsave() && !fx_only) { - if (copy_sigframe_from_user_to_xstate(fpu->fpstate, buf_fx)) + if (copy_sigframe_from_user_to_xstate(tsk, buf_fx)) return false; } else { if (__copy_from_user(&fpregs->fxsave, buf_fx, diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index c8340156bfd2..8f14981a3936 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1197,7 +1197,7 @@ static int copy_from_buffer(void *dst, unsigned int offset, unsigned int size, static int copy_uabi_to_xstate(struct fpstate *fpstate, const void *kbuf, - const void __user *ubuf) + const void __user *ubuf, u32 *pkru) { struct xregs_state *xsave = &fpstate->regs.xsave; unsigned int offset, size; @@ -1246,6 +1246,21 @@ static int copy_uabi_to_xstate(struct fpstate *fpstate, const void *kbuf, } } + /* + * Update the user protection key storage. Allow KVM to + * pass in a NULL pkru pointer if the mask bit is unset + * for its legacy ABI behavior. + */ + if (pkru) + *pkru = 0; + + if (hdr.xfeatures & XFEATURE_MASK_PKRU) { + struct pkru_state *xpkru; + + xpkru = __raw_xsave_addr(xsave, XFEATURE_PKRU); + *pkru = xpkru->pkru; + } + /* * The state that came in from userspace was user-state only. * Mask all the user states out of 'xfeatures': @@ -1264,9 +1279,9 @@ static int copy_uabi_to_xstate(struct fpstate *fpstate, const void *kbuf, * Convert from a ptrace standard-format kernel buffer to kernel XSAVE[S] * format and copy to the target thread. Used by ptrace and KVM. */ -int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf) +int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf, u32 *pkru) { - return copy_uabi_to_xstate(fpstate, kbuf, NULL); + return copy_uabi_to_xstate(fpstate, kbuf, NULL, pkru); } /* @@ -1274,10 +1289,10 @@ int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf) * XSAVE[S] format and copy to the target thread. This is called from the * sigreturn() and rt_sigreturn() system calls. */ -int copy_sigframe_from_user_to_xstate(struct fpstate *fpstate, +int copy_sigframe_from_user_to_xstate(struct task_struct *tsk, const void __user *ubuf) { - return copy_uabi_to_xstate(fpstate, NULL, ubuf); + return copy_uabi_to_xstate(tsk->thread.fpu.fpstate, NULL, ubuf, &tsk->thread.pkru); } static bool validate_independent_components(u64 mask) diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h index 5ad47031383b..a4ecb04d8d64 100644 --- a/arch/x86/kernel/fpu/xstate.h +++ b/arch/x86/kernel/fpu/xstate.h @@ -46,8 +46,8 @@ extern void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate, u32 pkru_val, enum xstate_copy_mode copy_mode); extern void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk, enum xstate_copy_mode mode); -extern int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf); -extern int copy_sigframe_from_user_to_xstate(struct fpstate *fpstate, const void __user *ubuf); +extern int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf, u32 *pkru); +extern int copy_sigframe_from_user_to_xstate(struct task_struct *tsk, const void __user *ubuf); extern void fpu__init_cpu_xstate(void);