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Mon, 17 Mar 2025 09:21:17 +0100 Received: from pty.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::c5]) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1tu5im-000DEo-2K; Mon, 17 Mar 2025 09:21:17 +0100 Received: from sha by pty.whiteo.stw.pengutronix.de with local (Exim 4.96) (envelope-from ) id 1tu5in-00158M-02; Mon, 17 Mar 2025 09:21:17 +0100 Date: Mon, 17 Mar 2025 09:21:16 +0100 From: Sascha Hauer To: Ahmad Fatoum Cc: barebox@lists.infradead.org, Adrian Negreanu Message-ID: References: <20250313101728.3546902-1-a.fatoum@pengutronix.de> <20250313101728.3546902-6-a.fatoum@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250313101728.3546902-6-a.fatoum@pengutronix.de> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250317_012118_986991_EB26796E X-CRM114-Status: GOOD ( 18.27 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-5.4 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 05/11] fs: add qemu_fw_cfg file system X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) Hi Ahmad, On Thu, Mar 13, 2025 at 11:17:22AM +0100, Ahmad Fatoum wrote: > +static int fw_cfg_fs_io(struct device *dev, struct file *f, void *buf, > + size_t insize, bool read) > +{ > + struct inode *inode = f->f_inode; > + struct fw_cfg_fs_inode *node = inode_to_node(inode); > + struct fw_cfg_fs_data *data = dev->priv; > + int fd = data->fd; > + > + if (node->buf) { > + if (read) > + memcpy(buf, node->buf + f->f_pos, insize); > + else > + memcpy(node->buf + f->f_pos, buf, insize); > + return insize; > + } > + > + ioctl(fd, FW_CFG_SELECT, &(u16) { inode->i_ino }); > + > + if (read) > + return pread(fd, buf, insize, f->f_pos); > + else > + return pwrite(fd, buf, insize, f->f_pos); > +} > + > +static int fw_cfg_fs_read(struct device *dev, struct file *f, void *buf, > + size_t insize) > +{ > + return fw_cfg_fs_io(dev, f, buf, insize, true); > +} > + > +static int fw_cfg_fs_write(struct device *dev, struct file *f, const void *buf, > + size_t insize) > +{ > + return fw_cfg_fs_io(dev, f, (void *)buf, insize, false); > +} > + > +static int fw_cfg_fw_truncate(struct device *dev, struct file *f, loff_t size) > +{ > + return 0; > +} By returning 0 here you claim that the file can get an arbitrary size. node->buf is a fixed size buffer. If I understand correctly then node->buf is only used for special files like "name", "raw". However, writing to these files is not prohibited, consequently a cp /dev/ram0 /mnt/fw_cfg//by_key/37/key results in memory corrupions. Writing data to a file I passed via --env truncates the file to the written data size, but the actual content of the file is unchanged. I still read back the original data. Is writing data supported? Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |