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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 15F25C35FFA for ; Wed, 19 Mar 2025 14:30:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=vEEkoiFhJTTNltysI4HnUNrjjey/OwLRpiIq5KPrSIs=; b=fMd/XR8bqq75cMlMgduQXXEyzH hSlvLePd5F/x8JsbFZiZv3uT9BOHruFyIoO8/KizLsb/i05XPrJZBKrFRG4QAQG8BUzHxsPSDoaKA mDaXmLx1kYzFfmBH8KTxmqcoZfc4vRq3eymyPa3h71tIUqNIaDMrA7MVSdCQz/wYDkSu9GKkVM53u hGXFqJY7DQ45VmKvwkOG9vjssznemvZYUmZ+kI4Hj8Br7Mx8BZA3vQF2NLGBUExKTY83jpLElBjaE YdmFC5yQ5eSMh7Ad0sQWNDdOE2AM+CWTurlCBWGbl7AclxtUm+vT+15zLFFyyCHzq7CWNkej+YAOW XlvV3y6Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tuuQk-00000009DEz-1LR2; Wed, 19 Mar 2025 14:30:02 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tuuNP-00000009Cg6-46LN for linux-arm-kernel@lists.infradead.org; Wed, 19 Mar 2025 14:26:37 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E07B0FEC; Wed, 19 Mar 2025 07:26:42 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9B0373F673; Wed, 19 Mar 2025 07:26:31 -0700 (PDT) Date: Wed, 19 Mar 2025 14:26:26 +0000 From: Mark Rutland To: Jeremy Linton Cc: linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, mhiramat@kernel.org, oleg@redhat.com, peterz@infradead.org, acme@kernel.org, namhyung@kernel.org, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, thiago.bauermann@linaro.org, broonie@kernel.org, yury.khrustalev@arm.com, kristina.martsenko@arm.com, liaochang1@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/7] arm64/gcs: task_gcs_el0_enable() should use passed task Message-ID: References: <20250318204841.373116-1-jeremy.linton@arm.com> <20250318204841.373116-2-jeremy.linton@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250318204841.373116-2-jeremy.linton@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250319_072636_057425_C6674CC8 X-CRM114-Status: GOOD ( 18.95 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Mar 18, 2025 at 03:48:35PM -0500, Jeremy Linton wrote: > Mark Rutland noticed that the task parameter is ignored and > 'current' is being used instead. Since this is usually > what its passed, it hasn't yet been causing problems but likely > will as the code gets more testing. Are we sure nothing is relying upon the bug? For example, in copy_thread_gcs(): copy_thread_gcs(p, ...) { ... gcs = gcs_alloc_thread_stack(p, ...) { ... if (!task_gcs_el0_enabled(p)) return 0; ... < actually allocate here > } ... p->thread.gcs_el0_mode = current->thread.gcs_el0_mode; ... } Either that later assignment is redundant, or copy_thread_gcs() was accidentally relying upon task_gcs_el0_enabled() reading from 'current' rather than 'p', and this change opens up another bug... Mark. > > Fixes: fc84bc5378a8 ("arm64/gcs: Context switch GCS state for EL0") > Signed-off-by: Jeremy Linton > --- > arch/arm64/include/asm/gcs.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/gcs.h b/arch/arm64/include/asm/gcs.h > index f50660603ecf..5bc432234d3a 100644 > --- a/arch/arm64/include/asm/gcs.h > +++ b/arch/arm64/include/asm/gcs.h > @@ -58,7 +58,7 @@ static inline u64 gcsss2(void) > > static inline bool task_gcs_el0_enabled(struct task_struct *task) > { > - return current->thread.gcs_el0_mode & PR_SHADOW_STACK_ENABLE; > + return task->thread.gcs_el0_mode & PR_SHADOW_STACK_ENABLE; > } > > void gcs_set_el0_mode(struct task_struct *task); > -- > 2.48.1 >