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 C20705A7A1 for ; Wed, 31 Jan 2024 15:14:21 +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=1706714063; cv=none; b=uIGA9/LRY0Akx4+SMb7BAVfE4qzwCewLDOcC7NXOrHw3deZX3fNI43sGOre4IERIDivmIis9jiWcPFlgIVaQRXMw60hmPad4VwLG+b9V56ggpR/jvjTKNuR2TFZkj8lwWi9r2ehrSl1siDhkm+vZGzplnGOuXTe3cjKpF0Pi9eg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706714063; c=relaxed/simple; bh=/qhuO5HuYtAvq48p1CcziTjf7g4yt0baC+LPUKnS3Yw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IMlMH9BcdeKdzgn4N55rPcQcZd+0nY95wPo9eJ2jfdwa7EGl/4n3ImPb9afjxZDciKkiAM9jM9haCZE0ZIdBvI6KJvfRqBahESXfFYJ7Z3ogAjQdZJ2wl0DjrFs5jZabPZeKg7Si0xyICPzUt1fmEJ9nEbWxUf0Tm76j6uRByOk= 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 8FD83DA7; Wed, 31 Jan 2024 07:15:04 -0800 (PST) Received: from [10.1.196.40] (e121345-lin.cambridge.arm.com [10.1.196.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4E5703F762; Wed, 31 Jan 2024 07:14:20 -0800 (PST) Message-ID: Date: Wed, 31 Jan 2024 15:14:18 +0000 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] swiotlb: Enforce page alignment in swiotlb_alloc() Content-Language: en-GB To: Will Deacon , linux-kernel@vger.kernel.org Cc: kernel-team@android.com, iommu@lists.linux.dev, Christoph Hellwig , Marek Szyprowski , Petr Tesarik , Dexuan Cui References: <20240131122543.14791-1-will@kernel.org> <20240131122543.14791-3-will@kernel.org> From: Robin Murphy In-Reply-To: <20240131122543.14791-3-will@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 31/01/2024 12:25 pm, Will Deacon wrote: > When allocating pages from a restricted DMA pool in swiotlb_alloc(), > the buffer address is blindly converted to a 'struct page *' that is > returned to the caller. In the unlikely event of an allocation bug, > page-unaligned addresses are not detected and slots can silently be > double-allocated. > > Add a simple check of the buffer alignment in swiotlb_alloc() to make > debugging a little easier if something has gone wonky. > > Cc: Christoph Hellwig > Cc: Marek Szyprowski > Cc: Robin Murphy > Cc: Petr Tesarik > Cc: Dexuan Cui > Signed-off-by: Will Deacon > --- > kernel/dma/swiotlb.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 56cc08b1fbd6..4485f216e620 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -1642,6 +1642,12 @@ struct page *swiotlb_alloc(struct device *dev, size_t size) > return NULL; > > tlb_addr = slot_addr(pool->start, index); > + if (unlikely(!PAGE_ALIGNED(tlb_addr))) { > + dev_WARN_ONCE(dev, 1, "Cannot allocate pages from non page-aligned swiotlb addr 0x%pa.\n", > + &tlb_addr); Nit: if there's cause for another respin, I'd be inclined to use a straightforward "if (WARN_ON(...))" here - this condition should represent SWIOTLB itself going badly wrong, which isn't really attributable to whatever device happened to be involved in the call. Cheers, Robin. > + swiotlb_release_slots(dev, tlb_addr); > + return NULL; > + } > > return pfn_to_page(PFN_DOWN(tlb_addr)); > }