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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net: usb: dm9601: fix wrong return value in dm9601_mdio_read Message-ID: <20240227160918.GB277116@kernel.org> References: <20240225-dm9601_ret_err-v1-1-02c1d959ea59@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20240225-dm9601_ret_err-v1-1-02c1d959ea59@gmail.com> On Sun, Feb 25, 2024 at 12:20:06AM +0100, Javier Carrasco wrote: > The MII code does not check the return value of mdio_read (among > others), and therefore no error code should be sent. A previous fix to > the use of an uninitialized variable propagates negative error codes, > that might lead to wrong operations by the MII library. > > An example of such issues is the use of mii_nway_restart by the dm9601 > driver. The mii_nway_restart function does not check the value returned > by mdio_read, which in this case might be a negative number which could > contain the exact bit the function checks (BMCR_ANENABLE = 0x1000). > > Return zero in case of error, as it is common practice in users of > mdio_read to avoid wrong uses of the return value. > > Fixes: 8f8abb863fa5 ("net: usb: dm9601: fix uninitialized variable use in dm9601_mdio_read") > Signed-off-by: Javier Carrasco I guess it would be nice if error values could be used, but as you have described, that does not seem to be the case here. Reviewed-by: Simon Horman