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 3318E22611 for ; Sun, 30 Mar 2025 07:31:46 +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=1743319908; cv=none; b=iSYm5JmYoCX4lpcOqkGDJfVJb1nYPA1qLTy7PLoAs4mt7rjQF10idmkEP/ObwLMFW0RnXsxSjlgy0/W7T3mK40A6+M9kJRKpy1qhc5vigpCzADSXMobWJJXu6A5+jhPxGuSx8q/NSGpHagfqfdFsGYL3J30hLJUJ1vxw9Mz5NCI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743319908; c=relaxed/simple; bh=0P43/VJZizLB00/Wzp2FmSM07nhoI88bGgfM5SzNu7A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uLsWbrm+/dvkb2vo4WJ0bzQqsfpFNqnLDittYV4+AajJsvwyalY/Ze7Y/hfAyTYqwmuXJbRSriUBoFYwE31eOPms7afrL3NLoJbs67BwzBqE5vn78aO0WP1X/tDzbOmnzvSEx9CMwHhMveALXu/TBPRKUIM8XT1IxPeBCohh8gA= 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 885AD1007; Sun, 30 Mar 2025 00:31:50 -0700 (PDT) Received: from [10.163.71.186] (unknown [10.163.71.186]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 409C23F694; Sun, 30 Mar 2025 00:31:39 -0700 (PDT) Message-ID: Date: Sun, 30 Mar 2025 13:01:36 +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] arm64: pageattr: Explicitly bail out when changing permissions for vmalloc_huge mappings To: Ryan Roberts , Mike Rapoport Cc: catalin.marinas@arm.com, will@kernel.org, gshan@redhat.com, steven.price@arm.com, suzuki.poulose@arm.com, tianyaxiong@kylinos.cn, ardb@kernel.org, david@redhat.com, urezki@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20250328062103.79462-1-dev.jain@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 29/03/25 3:16 pm, Ryan Roberts wrote: > On 28/03/2025 18:50, Mike Rapoport wrote: >> On Fri, Mar 28, 2025 at 11:51:03AM +0530, Dev Jain wrote: >>> arm64 uses apply_to_page_range to change permissions for kernel VA mappings, >> >> for vmalloc mappings ^ >> >> arm64 does not allow changing permissions to any VA address right now. >> >>> which does not support changing permissions for leaf mappings. This function >>> will change permissions until it encounters a leaf mapping, and will bail >>> out. To avoid this partial change, explicitly disallow changing permissions >>> for VM_ALLOW_HUGE_VMAP mappings. >>> >>> Signed-off-by: Dev Jain > > I wonder if we want a Fixes: tag here? It's certainly a *latent* bug. I am struggling to find the commit till which we want to backport. Should it be e920722 (arm64: support huge vmalloc mappings)? > >>> --- >>> arch/arm64/mm/pageattr.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c >>> index 39fd1f7ff02a..8337c88eec69 100644 >>> --- a/arch/arm64/mm/pageattr.c >>> +++ b/arch/arm64/mm/pageattr.c >>> @@ -96,7 +96,7 @@ static int change_memory_common(unsigned long addr, int numpages, >>> * we are operating on does not result in such splitting. >>> * >>> * Let's restrict ourselves to mappings created by vmalloc (or vmap). >>> - * Those are guaranteed to consist entirely of page mappings, and >>> + * Disallow VM_ALLOW_HUGE_VMAP vmalloc mappings so that >> >> I'd keep mention of page mappings in the comment, e.g >> >> * Disallow VM_ALLOW_HUGE_VMAP mappings to guarantee that only page >> * mappings are updated and splitting is never needed. >> >> With this and changelog updates Ryan asked for >> >> Reviewed-by: Mike Rapoport (Microsoft) >> >> >>> * splitting is never needed. >>> * >>> * So check whether the [addr, addr + size) interval is entirely >>> @@ -105,7 +105,7 @@ static int change_memory_common(unsigned long addr, int numpages, >>> area = find_vm_area((void *)addr); >>> if (!area || >>> end > (unsigned long)kasan_reset_tag(area->addr) + area->size || >>> - !(area->flags & VM_ALLOC)) >>> + ((area->flags & (VM_ALLOC | VM_ALLOW_HUGE_VMAP)) != VM_ALLOC)) >>> return -EINVAL; >>> >>> if (!numpages) >>> -- >>> 2.30.2 >>> >> >