From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CFE4725D8F6; Tue, 25 Mar 2025 12:38:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742906323; cv=none; b=KkBxutkXbbVc587lZvMgVLgbGPjiJRJLij3/WhqCyBSNhpk+BFZl1dSba44xR1AVzn6nbeQR8sdLBCXcMt8qP/d/2Y9URDRvBLgYVrUdewQyB8+8caqHsLn/IqGhpFe4wlWrTuvqOEdrC9UvUx0NWo0+VEmhTNj0p3dxeCFtzp4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742906323; c=relaxed/simple; bh=TLl0zf+hkOIQmCVmNyC1DiJ0WR+//OpPzQF+W8ph4Lk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qz39LksGS338/Jk1gP2zdf0dxgE/yzAjnyrrO7X8NYNQgQe1j0q28GD9yVfCat1qednH/85GMgII18fXtuVux+pH6Gcujk50Hxm3cg8YVNxGx7cjBv0uV9LOdj3wnfgCUCWuq+yy+ymEknB8dnDtpa5/MFF3B3anFUDuG6XODvg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=lc+VZoDc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="lc+VZoDc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60DC3C4CEE4; Tue, 25 Mar 2025 12:38:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1742906323; bh=TLl0zf+hkOIQmCVmNyC1DiJ0WR+//OpPzQF+W8ph4Lk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lc+VZoDcnLu2Eb4J71dbvpeuMxAsXojK1Ow/fnX0TSKjGnZx+eNDfuZu1uYgi0QJP S79bTqIe6318nNs0L2/dMLVAk45YGl5HHocS3troM2tSLpiTDUwszp42I8+mvXOr9V fH/1S2QA6zk1xtEpfeg8EvPE4857sneuUIvWNvBw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+d7d8c418e8317899e88c@syzkaller.appspotmail.com, Vincent Mailhol , Marc Kleine-Budde Subject: [PATCH 6.12 056/116] can: ucan: fix out of bound read in strscpy() source Date: Tue, 25 Mar 2025 08:22:23 -0400 Message-ID: <20250325122150.642033080@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250325122149.207086105@linuxfoundation.org> References: <20250325122149.207086105@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vincent Mailhol commit 1d22a122ffb116c3cf78053e812b8b21f8852ee9 upstream. Commit 7fdaf8966aae ("can: ucan: use strscpy() to instead of strncpy()") unintentionally introduced a one byte out of bound read on strscpy()'s source argument (which is kind of ironic knowing that strscpy() is meant to be a more secure alternative :)). Let's consider below buffers: dest[len + 1]; /* will be NUL terminated */ src[len]; /* may not be NUL terminated */ When doing: strncpy(dest, src, len); dest[len] = '\0'; strncpy() will read up to len bytes from src. On the other hand: strscpy(dest, src, len + 1); will read up to len + 1 bytes from src, that is to say, an out of bound read of one byte will occur on src if it is not NUL terminated. Note that the src[len] byte is never copied, but strscpy() still needs to read it to check whether a truncation occurred or not. This exact pattern happened in ucan. The root cause is that the source is not NUL terminated. Instead of doing a copy in a local buffer, directly NUL terminate it as soon as usb_control_msg() returns. With this, the local firmware_str[] variable can be removed. On top of this do a couple refactors: - ucan_ctl_payload->raw is only used for the firmware string, so rename it to ucan_ctl_payload->fw_str and change its type from u8 to char. - ucan_device_request_in() is only used to retrieve the firmware string, so rename it to ucan_get_fw_str() and refactor it to make it directly handle all the string termination logic. Reported-by: syzbot+d7d8c418e8317899e88c@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-can/67b323a4.050a0220.173698.002b.GAE@google.com/ Fixes: 7fdaf8966aae ("can: ucan: use strscpy() to instead of strncpy()") Signed-off-by: Vincent Mailhol Link: https://patch.msgid.link/20250218143515.627682-2-mailhol.vincent@wanadoo.fr Cc: stable@vger.kernel.org Signed-off-by: Marc Kleine-Budde Signed-off-by: Greg Kroah-Hartman --- drivers/net/can/usb/ucan.c | 43 ++++++++++++++++++------------------------- 1 file changed, 18 insertions(+), 25 deletions(-) --- a/drivers/net/can/usb/ucan.c +++ b/drivers/net/can/usb/ucan.c @@ -186,7 +186,7 @@ union ucan_ctl_payload { */ struct ucan_ctl_cmd_get_protocol_version cmd_get_protocol_version; - u8 raw[128]; + u8 fw_str[128]; } __packed; enum { @@ -424,18 +424,20 @@ static int ucan_ctrl_command_out(struct UCAN_USB_CTL_PIPE_TIMEOUT); } -static int ucan_device_request_in(struct ucan_priv *up, - u8 cmd, u16 subcmd, u16 datalen) +static void ucan_get_fw_str(struct ucan_priv *up, char *fw_str, size_t size) { - return usb_control_msg(up->udev, - usb_rcvctrlpipe(up->udev, 0), - cmd, - USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE, - subcmd, - 0, - up->ctl_msg_buffer, - datalen, - UCAN_USB_CTL_PIPE_TIMEOUT); + int ret; + + ret = usb_control_msg(up->udev, usb_rcvctrlpipe(up->udev, 0), + UCAN_DEVICE_GET_FW_STRING, + USB_DIR_IN | USB_TYPE_VENDOR | + USB_RECIP_DEVICE, + 0, 0, fw_str, size - 1, + UCAN_USB_CTL_PIPE_TIMEOUT); + if (ret > 0) + fw_str[ret] = '\0'; + else + strscpy(fw_str, "unknown", size); } /* Parse the device information structure reported by the device and @@ -1314,7 +1316,6 @@ static int ucan_probe(struct usb_interfa u8 in_ep_addr; u8 out_ep_addr; union ucan_ctl_payload *ctl_msg_buffer; - char firmware_str[sizeof(union ucan_ctl_payload) + 1]; udev = interface_to_usbdev(intf); @@ -1527,17 +1528,6 @@ static int ucan_probe(struct usb_interfa */ ucan_parse_device_info(up, &ctl_msg_buffer->cmd_get_device_info); - /* just print some device information - if available */ - ret = ucan_device_request_in(up, UCAN_DEVICE_GET_FW_STRING, 0, - sizeof(union ucan_ctl_payload)); - if (ret > 0) { - /* copy string while ensuring zero termination */ - strscpy(firmware_str, up->ctl_msg_buffer->raw, - sizeof(union ucan_ctl_payload) + 1); - } else { - strcpy(firmware_str, "unknown"); - } - /* device is compatible, reset it */ ret = ucan_ctrl_command_out(up, UCAN_COMMAND_RESET, 0, 0); if (ret < 0) @@ -1555,7 +1545,10 @@ static int ucan_probe(struct usb_interfa /* initialisation complete, log device info */ netdev_info(up->netdev, "registered device\n"); - netdev_info(up->netdev, "firmware string: %s\n", firmware_str); + ucan_get_fw_str(up, up->ctl_msg_buffer->fw_str, + sizeof(up->ctl_msg_buffer->fw_str)); + netdev_info(up->netdev, "firmware string: %s\n", + up->ctl_msg_buffer->fw_str); /* success */ return 0;