From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A2FB200AC; Mon, 9 Oct 2023 20:48:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [IPv6:2001:4b98:dc4:8::226]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9758692; Mon, 9 Oct 2023 13:48:40 -0700 (PDT) Received: by mail.gandi.net (Postfix) with ESMTPSA id E6FD4C0002; Mon, 9 Oct 2023 20:48:36 +0000 (UTC) Received: from peko by dell.be.48ers.dk with local (Exim 4.94.2) (envelope-from ) id 1qpxB0-00FbYD-V5; Mon, 09 Oct 2023 22:48:30 +0200 From: Peter Korsgaard To: Javier Carrasco Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , syzbot+1f53a30781af65d2c955@syzkaller.appspotmail.com, netdev@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net: usb: dm9601: fix uninitialized variable use in dm9601_mdio_read References: <20231009-topic-dm9601_uninit_mdio_read-v1-1-d4d775e24e3b@gmail.com> Date: Mon, 09 Oct 2023 22:48:30 +0200 In-Reply-To: <20231009-topic-dm9601_uninit_mdio_read-v1-1-d4d775e24e3b@gmail.com> (Javier Carrasco's message of "Mon, 09 Oct 2023 20:52:55 +0200") Message-ID: <87zg0rcyjl.fsf@48ers.dk> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-GND-Sasl: peter@korsgaard.com X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net >>>>> "Javier" == Javier Carrasco writes: > syzbot has found an uninit-value bug triggered by the dm9601 driver [1]. > This error happens because the variable res is not updated if the call > to dm_read_shared_word returns an error or if no data is read (see > __usbnet_read_cmd()). In this particular case -EPROTO was returned and > res stayed uninitialized. > This can be avoided by checking the return value of dm_read_shared_word > and returning an error if the read operation failed or no data was read. > [1] https://syzkaller.appspot.com/bug?extid=1f53a30781af65d2c955 > Signed-off-by: Javier Carrasco > Reported-and-tested-by: syzbot+1f53a30781af65d2c955@syzkaller.appspotmail.com > --- > drivers/net/usb/dm9601.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > diff --git a/drivers/net/usb/dm9601.c b/drivers/net/usb/dm9601.c > index 48d7d278631e..e223daa93229 100644 > --- a/drivers/net/usb/dm9601.c > +++ b/drivers/net/usb/dm9601.c > @@ -222,13 +222,20 @@ static int dm9601_mdio_read(struct net_device *netdev, int phy_id, int loc) > struct usbnet *dev = netdev_priv(netdev); > __le16 res; > + int err; > if (phy_id) { > netdev_dbg(dev->net, "Only internal phy supported\n"); > return 0; > } > - dm_read_shared_word(dev, 1, loc, &res); > + err = dm_read_shared_word(dev, 1, loc, &res); > + if (err <= 0) { > + if (err == 0) > + err = -ENODATA; Looking at dm_read(), it doesn't look like we can end up here with err == 0, but OK. Acked-by: Peter Korsgaard -- Bye, Peter Korsgaard