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[83.28.46.53]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488c5db33b4sm17711325e9.6.2026.04.08.01.33.45 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Wed, 08 Apr 2026 01:33:46 -0700 (PDT) Date: Wed, 8 Apr 2026 10:33:43 +0200 From: Michal Pecio To: Andrew Lunn Cc: Petko Manolov , Simon Horman , Morduan Zang , Andrew Lunn , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-usb@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+9db6c624635564ad813c@syzkaller.appspotmail.com Subject: Re: [PATCH] usb: rtl8150: avoid using uninitialized CSCR value Message-ID: <20260408103343.19cf599a.michal.pecio@gmail.com> In-Reply-To: <76d6b341-27d5-44aa-92fb-3b8966d609df@lunn.ch> References: <93FF85BB9F33CD2B+20260402070743.20641-1-zhangdandan@uniontech.com> <20260403154538.GA187715@horms.kernel.org> <20260405085212.GA8491@cabron.k.g> <76d6b341-27d5-44aa-92fb-3b8966d609df@lunn.ch> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 6 Apr 2026 01:38:06 +0200, Andrew Lunn wrote: > > > - get_registers(dev, CSCR, 2, &tmp); > > > + if (get_registers(dev, CSCR, 2, &tmp) < 0) > > > + tmp = 0; > > > if (tmp & CSCR_LINK_STATUS) > > > netif_carrier_on(netdev); > > > else > > > > I was wondering if calling netif_carrier_off() is the right thing > > to do in case get_registers() fail. > > > > There are multiple get_registers() calls that don't check the error > > and if we do this in set_carrier() maybe we should do the same > > thing across the whole driver? > > What does it actually mean if get_registers() fails? The device is > gone? Hot unplugged? If so, you are going to get a cascade of errors, > and then hopefully the USB core code removes the device? > > Are there any legitimate reasons for get_registers() to fail if the > device is still plugged in? In principle it might be temporary EMI or a flaky cable. These errors rarely reach drivers due to retries in USB layer, but in extreme cases the device may be in unknown state and it may become functional later. IIRC net layer has some operations which are presumed trivial enough that they would never fail, so this could be annoying. It does seem rare enough in practice that for 25 years nobody noticed carrier status being set to a random vaule by this driver. BTW, some functions like rtl8150_reset() pre-set data to a value which will be safe in case of get_register() failure. But here, unhandled set_register() error is dodgy - the 0x10 bit may never turn on. Regards, Michal