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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F205FC433EF for ; Fri, 1 Oct 2021 22:45:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF22161AFD for ; Fri, 1 Oct 2021 22:45:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356226AbhJAWrJ (ORCPT ); Fri, 1 Oct 2021 18:47:09 -0400 Received: from mga17.intel.com ([192.55.52.151]:38094 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230376AbhJAWql (ORCPT ); Fri, 1 Oct 2021 18:46:41 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10124"; a="205756649" X-IronPort-AV: E=Sophos;i="5.85,340,1624345200"; d="scan'208";a="205756649" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Oct 2021 15:44:22 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.85,340,1624345200"; d="scan'208";a="565343997" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga002.fm.intel.com with ESMTP; 01 Oct 2021 15:44:16 -0700 From: "Chang S. Bae" To: bp@suse.de, luto@kernel.org, tglx@linutronix.de, mingo@kernel.org, x86@kernel.org Cc: len.brown@intel.com, lenb@kernel.org, dave.hansen@intel.com, thiago.macieira@intel.com, jing2.liu@intel.com, ravi.v.shankar@intel.com, linux-kernel@vger.kernel.org, chang.seok.bae@intel.com Subject: [PATCH v11 14/29] x86/fpu/xstate: Support ptracer-induced XSTATE buffer expansion Date: Fri, 1 Oct 2021 15:37:13 -0700 Message-Id: <20211001223728.9309-15-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20211001223728.9309-1-chang.seok.bae@intel.com> References: <20211001223728.9309-1-chang.seok.bae@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ptrace() may update XSTATE data before the target task has taken an XFD fault and expanded the XSTATE buffer. Detect this case and allocate a sufficient buffer to support the request. Also, disable the (now unnecessary) associated first-use fault. Signed-off-by: Chang S. Bae Reviewed-by: Len Brown Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v9: * Simplify the code further. (Borislav Petkov) Changes from v5: * Adjusted to use 'tmpbuf' for the new base code. Changes from v4: * Improved the condition check for the expansion. * Simplified the XSTATE_BV retrieval. * Updated the code comment. Changes from v3: * Removed 'no functional changes' in the changelog. (Borislav Petkov) Changes from v2: * Updated the changelog with task->fpu removed. (Borislav Petkov) * Updated the code comments. --- arch/x86/kernel/fpu/regset.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index 7ea10f98c2b0..c57ad37a95fe 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -163,6 +163,27 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset, } } + /* + * When a ptracer attempts to write any dynamic user state in the + * target buffer but not sufficiently allocated, it dynamically + * expands the buffer. + */ + if (xfeatures_mask_user_dynamic) { + u64 state_mask; + + /* Retrieve XSTATE_BV. */ + memcpy(&state_mask, (kbuf ?: tmpbuf) + offsetof(struct xregs_state, header), + sizeof(u64)); + + /* Expand the xstate buffer based on the XSTATE_BV. */ + state_mask &= xfeatures_mask_user_dynamic; + if (state_mask) { + ret = realloc_xstate_buffer(fpu, state_mask); + if (ret) + goto out; + } + } + fpu_force_restore(fpu); ret = copy_uabi_from_kernel_to_xstate(fpu, kbuf ?: tmpbuf); -- 2.17.1