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Sat, 12 Apr 2025 11:30:52 -0700 (PDT) Received: from qasdev.system ([2a02:c7c:6696:8300:f069:f1cb:5bbc:db26]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39eaf445315sm5699769f8f.82.2025.04.12.11.30.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 12 Apr 2025 11:30:51 -0700 (PDT) Date: Sat, 12 Apr 2025 19:30:36 +0100 From: Qasim Ijaz To: Andrew Lunn Cc: Jakub Kicinski , andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, horms@kernel.org, linux-usb@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot Subject: Re: [PATCH 1/4] net: fix uninitialised access in mii_nway_restart() Message-ID: References: <20250319112156.48312-1-qasdev00@gmail.com> <20250319112156.48312-2-qasdev00@gmail.com> <20250325063307.15336182@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Apr 11, 2025 at 03:12:06AM +0200, Andrew Lunn wrote: > On Thu, Apr 10, 2025 at 11:15:23PM +0100, Qasim Ijaz wrote: > > On Tue, Mar 25, 2025 at 06:33:07AM -0700, Jakub Kicinski wrote: > > > On Wed, 19 Mar 2025 11:21:53 +0000 Qasim Ijaz wrote: > > > > --- a/drivers/net/mii.c > > > > +++ b/drivers/net/mii.c > > > > @@ -464,6 +464,8 @@ int mii_nway_restart (struct mii_if_info *mii) > > > > > > > > /* if autoneg is off, it's an error */ > > > > bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR); > > > > + if (bmcr < 0) > > > > + return bmcr; > > > > > > > > if (bmcr & BMCR_ANENABLE) { > > > > bmcr |= BMCR_ANRESTART; > > > > > > We error check just one mdio_read() but there's a whole bunch of them > > > in this file. What's the expected behavior then? Are all of them buggy? > > > > > > > Hi Jakub > > > > Apologies for my delayed response, I had another look at this and I > > think my patch may be off a bit. You are correct that there are multiple > > mdio_read() calls and looking at the mii.c file we can see that calls to > > functions like mdio_read (and a lot of others) dont check return values. > > > > So in light of this I think a better patch would be to not edit the > > mii.c file at all and just make ch9200_mdio_read return 0 on > > error. > > Do you actually have one of these devices? If you do have, an even > better change would be to throwaway the mii code and swap to phylib > and an MDIO bus. You can probably follow smsc95xx.c. > Hi Andrew, Thanks for the suggestion. I don't have one of these devices at the moment. If in the future if I do I will definitely explore the suggestion more. Regards, Qasim > Andrew