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,URIBL_BLOCKED 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 BF2B8C47083 for ; Wed, 2 Jun 2021 16:01:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C0036157E for ; Wed, 2 Jun 2021 16:01:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232363AbhFBQDD (ORCPT ); Wed, 2 Jun 2021 12:03:03 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:40798 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229618AbhFBQC6 (ORCPT ); Wed, 2 Jun 2021 12:02:58 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1622649673; 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: in-reply-to:in-reply-to:references:references; bh=36dsNpISSMuXFqYfQPbjUuPj07IxMjRA/6SmqodzER8=; b=QqKvEHSMqnGN1n0adovTmdj9SDIpBdhK+u2GyiDzNgTX6DdviDl9nYELyZp1cgbfONvLPN 2SnjonKF5B6k/TVt8cUA9A3o14FvoEHOfXPJFGamyeqQ33vB5BrRwTR4v86yBLh0mPtWsN Pdh80MJwNLRSxwO3ojNSMzxCtKYeCmaaV8UJVvrCrUGUs8l0QUanhjbKkO1vv/2rLnaFAm SOya/UwN35DUA+wwPY672sjuVn4AtpnyKIFO0xB1j8lfMItkPeg1vxzFJisesa65LPPGiw 4rbqpYNMh9HwYq1bhLovh0zb/AZslaKIv5WjQnXTDONQ0WUaSrmxtwIc/TIthQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1622649673; 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: in-reply-to:in-reply-to:references:references; bh=36dsNpISSMuXFqYfQPbjUuPj07IxMjRA/6SmqodzER8=; b=DWIiNcJZQPpQ5FTTQlIiksa7x/TYhb+DyyonYIfmvHaXDBrAPSwRHLM8JrUotSkyQD8vYi jomYlO+wxEPbwxCA== To: LKML Cc: x86@kernel.org, Andy Lutomirski , Dave Hansen , Fenghua Yu , Tony Luck , Yu-cheng Yu Subject: [patch V2 5/8] x86/fpu: Sanitize xstateregs_set() In-Reply-To: <20210602101618.851242793@linutronix.de> References: <20210602095543.149814064@linutronix.de> <20210602101618.851242793@linutronix.de> Date: Wed, 02 Jun 2021 18:01:13 +0200 Message-ID: <87sg20z25y.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org xstateregs_set() operates on a stopped task and tries to copy the provided buffer into the tasks fpu.state.xsave buffer. Any error while copying or invalid state detected after copying results in wiping the target tasks FPU state completely including supervisor states. That's just wrong. The caller supplied invalid data or has a problem with unmapped memory, so there is absolutely no justification to wreckage the target. Fix this with the following modifications: 1) If data has to be copied from userspace, allocate a buffer and copy from user first. 2) Use copy_kernel_to_xstate() unconditionally so that header checking works correctly. 3) Return on error without wreckaging the target state. This prevents corrupting supervisor states and lets the caller deal with the problem it caused in the first place. Make validate_user_xstate_header() static as this was the last user outside of xstate.c Signed-off-by: Thomas Gleixner --- V2: Move the validate_user_xstate_header() static here --- arch/x86/include/asm/fpu/xstate.h | 4 --- arch/x86/kernel/fpu/regset.c | 41 +++++++++++++++----------------------- arch/x86/kernel/fpu/xstate.c | 12 ++++++----- 3 files changed, 24 insertions(+), 33 deletions(-) --- a/arch/x86/include/asm/fpu/xstate.h +++ b/arch/x86/include/asm/fpu/xstate.h @@ -112,8 +112,4 @@ void copy_supervisor_to_kernel(struct xr void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask); void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask); - -/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */ -int validate_user_xstate_header(const struct xstate_header *hdr); - #endif --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -6,8 +6,12 @@ #include #include #include + +#include + #include + /* * The xstateregs_active() routine is the same as the regset_fpregs_active() routine, * as the "regset->n" for the xstate regset will be updated based on the feature @@ -107,8 +111,8 @@ int xstateregs_set(struct task_struct *t unsigned int pos, unsigned int count, const void *kbuf, const void __user *ubuf) { + struct xregs_state *xsave, *xbuf = NULL; struct fpu *fpu = &target->thread.fpu; - struct xregs_state *xsave; int ret; if (!boot_cpu_has(X86_FEATURE_XSAVE)) @@ -120,32 +124,21 @@ int xstateregs_set(struct task_struct *t if (pos != 0 || count != fpu_user_xstate_size) return -EFAULT; - xsave = &fpu->state.xsave; - - fpu__prepare_write(fpu); - - if (using_compacted_format()) { - if (kbuf) - ret = copy_kernel_to_xstate(xsave, kbuf); - else - ret = copy_user_to_xstate(xsave, ubuf); - } else { - ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1); - if (!ret) - ret = validate_user_xstate_header(&xsave->header); + if (!kbuf) { + xbuf = vmalloc(count); + if (!xbuf) + return -ENOMEM; + ret = user_regset_copyin(&pos, &count, NULL, &ubuf, xbuf, 0, -1); + if (ret) + goto out; } - /* - * mxcsr reserved bits must be masked to zero for security reasons. - */ - xsave->i387.mxcsr &= mxcsr_feature_mask; - - /* - * In case of failure, mark all states as init: - */ - if (ret) - fpstate_init(&fpu->state); + xsave = &fpu->state.xsave; + fpu__prepare_write(fpu); + ret = copy_kernel_to_xstate(xsave, kbuf ? kbuf : xbuf); +out: + vfree(xbuf); return ret; } --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -515,7 +515,7 @@ int using_compacted_format(void) } /* Validate an xstate header supplied by userspace (ptrace or sigreturn) */ -int validate_user_xstate_header(const struct xstate_header *hdr) +static int validate_user_xstate_header(const struct xstate_header *hdr) { /* No unknown or supervisor features may be set */ if (hdr->xfeatures & ~xfeatures_mask_user()) @@ -1172,14 +1172,16 @@ int copy_kernel_to_xstate(struct xregs_s */ xsave->header.xfeatures |= hdr.xfeatures; + /* mxcsr reserved bits must be masked to zero for security reasons. */ + xsave->i387.mxcsr &= mxcsr_feature_mask; + return 0; } /* - * Convert from a ptrace or sigreturn standard-format user-space buffer to - * kernel XSAVES format and copy to the target thread. This is called from - * xstateregs_set(), as well as potentially from the sigreturn() and - * rt_sigreturn() system calls. + * Convert from a sigreturn standard-format user-space buffer to kernel + * XSAVES format and copy to the target thread. This is called from the + * sigreturn() and rt_sigreturn() system calls. */ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf) {