From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 338D9341ABB; Tue, 15 Sep 2026 04:41:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789447303; cv=none; b=Q5M62MLVkZj+EotquW7MsdB86aQiD3PgCR8SaGgBdAQYGbbLPW8FhGD8FBicHYnb0gNzLxXe1dyRrP04K95FBY3CLwnRYuyQVLhd4aeId2aNGtZIMJfwJOJ4D14x5jmeMLICv0LbkdgC8MfGa7egJXNVB/gr/n2J0ibvfOX1Zvg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789447303; c=relaxed/simple; bh=Ju8eEBCVHgcYCSDtTSvxH8+HI9wZGttAxQSi45Bswoc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=q0+AQmJHIuT5LOS5d091qcSya2lACkfWep/BlzhkLLU5Ch4Xu8fHoi2TYRUBvYQm1pnd6IRjg4/KUE3AITdjs7I7qAOH+FWxvUX43RsKpc5J6x4WVvm7HHseuoQ4/1ikPcFHjhlxgTDb6SfdWSSwvVTIObK4ylcZr9ObFRtd1pY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=YjiJYm9A; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="YjiJYm9A" Received: from [192.168.1.22] (unknown [4.194.122.162]) by linux.microsoft.com (Postfix) with ESMTPSA id DA0AA20B716B; Mon, 14 Sep 2026 21:40:54 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com DA0AA20B716B DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1789447257; bh=1sQehgbLWYGj+S+yUfXvdCI2TMes99MZjrcGwUzDaFs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YjiJYm9AWuNLhyRL5alheaXn+Bfd/lmJegRMmM3/oMbFAQdJmoZY6JQNOeRrLs7eL TG7KgQK7NncaysFM54SosVXffPki99wIxld/ueer5CBY0IvZvk/hh360emaosVYhx6 iTK31cg1lUAzqxVZ+OEgL1OdI5E0aJFPvV+NDZns= Message-ID: <3f771293-f5df-4e74-aca7-5d34966d00e0@linux.microsoft.com> Date: Tue, 15 Sep 2026 10:11:36 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mshv_vtl: Check per-CPU register page before mmap To: Hardik Garg , kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com Cc: mhklinux@outlook.com, ssengar@linux.microsoft.com, romank@linux.microsoft.com, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260911175146.1370148-1-hargar@linux.microsoft.com> Content-Language: en-US From: Naman Jain In-Reply-To: <20260911175146.1370148-1-hargar@linux.microsoft.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/11/2026 11:21 PM, Hardik Garg wrote: > Register-page setup is optional for each CPU. If allocation or > registration fails, mshv_vtl_configure_reg_page() warns and leaves that > CPU's reg_page NULL, but initial context setup continues successfully. > Meanwhile, successful setup on another CPU sets the global > mshv_has_reg_page flag. > > mshv_vtl_fault() checks this global flag before selecting the requested > CPU's register page. With mixed setup results across online CPUs, the > check passes even for a CPU with no register page, reaching > get_page(NULL) when userspace faults in that mapping. > > Check the selected per-CPU register page before taking its reference and > return VM_FAULT_SIGBUS if it is absent. > > Fixes: 7bfe3b8ea6e3 ("Drivers: hv: Introduce mshv_vtl driver") > Cc: stable@vger.kernel.org > Signed-off-by: Hardik Garg > --- > drivers/hv/mshv_vtl_main.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c > index fc993560a45c..3296ab5c0243 100644 > --- a/drivers/hv/mshv_vtl_main.c > +++ b/drivers/hv/mshv_vtl_main.c > @@ -912,6 +912,9 @@ static vm_fault_t mshv_vtl_fault(struct vm_fault *vmf) > return VM_FAULT_NOPAGE; > } > > + if (!page) > + return VM_FAULT_SIGBUS; > + > get_page(page); > vmf->page = page; > LGTM. Thanks. Reviewed-by: Naman Jain Regards, Naman