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Tue, 24 Mar 2026 04:03:39 -0700 (PDT) Received: from [192.168.88.32] ([212.105.153.60]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-487116c0c13sm83877085e9.7.2026.03.24.04.03.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Mar 2026 04:03:39 -0700 (PDT) Message-ID: Date: Tue, 24 Mar 2026 12:03:37 +0100 Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next] net: mana: Use at least SZ_4K in doorbell ID range check To: Simon Horman , Erni Sri Satya Vennela Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, longli@microsoft.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, shradhagupta@linux.microsoft.com, dipayanroy@linux.microsoft.com, shirazsaleem@microsoft.com, kotaranov@microsoft.com, yury.norov@gmail.com, kees@kernel.org, linux-hyperv@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260320122107.1560839-1-ernis@linux.microsoft.com> <20260321100425.GX74886@horms.kernel.org> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20260321100425.GX74886@horms.kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/21/26 11:04 AM, Simon Horman wrote: > On Fri, Mar 20, 2026 at 05:21:01AM -0700, Erni Sri Satya Vennela wrote: >> mana_gd_ring_doorbell() accesses doorbell offsets up to 0xFF8 + 8 = 4KB >> within a doorbell page. When db_page_size is zero, the validation check >> in mana_gd_register_device() reduces to: >> db_page_off + 0 > bar0_size >> which passes, even though mana_gd_ring_doorbell() will access >> [db_page_off, db_page_off + 4KB) and may go beyond BAR0. >> >> Use max(SZ_4K, db_page_size) in the range check so that a zero or >> unexpectedly small db_page_size still results in a rejection when the >> doorbell page would fall outside BAR0. > > Thanks Erni, > > I understand the maths here. And to that extent this change makes sense to me. > But I am curious to know how a db_page_size of zero works. I was expecting > some space is required there. To rephrase Simon's question, this feels like papering over a memory/state corruption. I think at best it deserves a cleaner explanation. /P