From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7599B33985; Wed, 19 Mar 2025 14:26:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742394398; cv=none; b=ujNdkuRTyQ+tarj7GZY6b4LHj1esgcSKHMdzyfKY9WpBJLBAPPfNU+nrtmFfd/rXdycDPQYR3q9r11R7Rsolc1U8GMBunCEQTDddkg3YWbnSelQ40sbJyBt3FDAxffiHEsH6Md0tWCcLEQqEP01gy2xflFc/39FPvUpWLRicp6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742394398; c=relaxed/simple; bh=6LaFCXWouUXetUyhtRcVc/74TIYXzXBLSNVMiDFBQcs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=l29t6KFVaXlY0G+4Px7Ck5GTjc4k3T3Fp2/FODG8hOUPqYLXDDjpwIL0cYBJ0YPuMhl1TIGPJY5EGj6BKYr85dNUzKA3IG9kXbsw61rZ7nqjiHWusmTViKssAbKyVx3eK8xbLqMi5mZSJRMYp6MTVwZdx40zs2mmdX6prXdIvF0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250318204841.373116-2-jeremy.linton@arm.com> 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 >