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[217.140.101.70]) by mx.google.com with ESMTP id s21si1109520edb.391.2019.03.25.07.08.40 for ; Mon, 25 Mar 2019 07:08:40 -0700 (PDT) Received-SPF: pass (google.com: domain of kevin.brodsky@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of kevin.brodsky@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 85E2A80D; Mon, 25 Mar 2019 07:08:39 -0700 (PDT) Received: from [10.1.199.35] (e107154-lin.cambridge.arm.com [10.1.199.35]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A2AE23F59C; Mon, 25 Mar 2019 07:08:31 -0700 (PDT) Subject: Re: [PATCH v13 17/20] media/v4l2-core, arm64: untag user pointers in videobuf_dma_contig_user_get To: Catalin Marinas , Andrey Konovalov Cc: Will Deacon , Mark Rutland , Robin Murphy , Kees Cook , Kate Stewart , Greg Kroah-Hartman , Andrew Morton , Ingo Molnar , "Kirill A . Shutemov" , Shuah Khan , Vincenzo Frascino , Eric Dumazet , "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Arnaldo Carvalho de Melo , Alex Deucher , =?UTF-8?Q?Christian_K=c3=b6nig?= , "David (ChunMing) Zhou" , Yishai Hadas , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Chintan Pandya , Luc Van Oostenryck , Dave Martin , Szabolcs Nagy References: <20190322160726.GV13384@arrakis.emea.arm.com> From: Kevin Brodsky Message-ID: Date: Mon, 25 Mar 2019 14:08:30 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: <20190322160726.GV13384@arrakis.emea.arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-GB X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 22/03/2019 16:07, Catalin Marinas wrote: > On Wed, Mar 20, 2019 at 03:51:31PM +0100, Andrey Konovalov wrote: >> This patch is a part of a series that extends arm64 kernel ABI to allow to >> pass tagged user pointers (with the top byte set to something else other >> than 0x00) as syscall arguments. >> >> videobuf_dma_contig_user_get() uses provided user pointers for vma >> lookups, which can only by done with untagged pointers. >> >> Untag the pointers in this function. >> >> Signed-off-by: Andrey Konovalov >> --- >> drivers/media/v4l2-core/videobuf-dma-contig.c | 9 +++++---- >> 1 file changed, 5 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/media/v4l2-core/videobuf-dma-contig.c b/drivers/media/v4l2-core/videobuf-dma-contig.c >> index e1bf50df4c70..8a1ddd146b17 100644 >> --- a/drivers/media/v4l2-core/videobuf-dma-contig.c >> +++ b/drivers/media/v4l2-core/videobuf-dma-contig.c >> @@ -160,6 +160,7 @@ static void videobuf_dma_contig_user_put(struct videobuf_dma_contig_memory *mem) >> static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem, >> struct videobuf_buffer *vb) >> { >> + unsigned long untagged_baddr = untagged_addr(vb->baddr); >> struct mm_struct *mm = current->mm; >> struct vm_area_struct *vma; >> unsigned long prev_pfn, this_pfn; >> @@ -167,22 +168,22 @@ static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem, >> unsigned int offset; >> int ret; >> >> - offset = vb->baddr & ~PAGE_MASK; >> + offset = untagged_baddr & ~PAGE_MASK; >> mem->size = PAGE_ALIGN(vb->size + offset); >> ret = -EINVAL; >> >> down_read(&mm->mmap_sem); >> >> - vma = find_vma(mm, vb->baddr); >> + vma = find_vma(mm, untagged_baddr); >> if (!vma) >> goto out_up; >> >> - if ((vb->baddr + mem->size) > vma->vm_end) >> + if ((untagged_baddr + mem->size) > vma->vm_end) >> goto out_up; >> >> pages_done = 0; >> prev_pfn = 0; /* kill warning */ >> - user_address = vb->baddr; >> + user_address = untagged_baddr; >> >> while (pages_done < (mem->size >> PAGE_SHIFT)) { >> ret = follow_pfn(vma, user_address, &this_pfn); > I don't think vb->baddr here is anonymous mmap() but worth checking the > call paths. I spent some time on this, I didn't find any restriction on the kind of mapping that's allowed here. The API regarding V4L2_MEMORY_USERPTR doesn't seem to say anything about that either [0] [1]. It's probably best to ask the V4L2 maintainers. Kevin [0] https://www.kernel.org/doc/html/latest/media/uapi/v4l/vidioc-qbuf.html [1] https://www.kernel.org/doc/html/latest/media/uapi/v4l/userp.html