From: Qasim Ijaz <qasdev00@gmail.com> stable inclusion from stable-v6.6.75 commit 6377838560c03b36e1153a42ef727533def9b68f category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBLDIN CVE: CVE-2025-21689 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 575a5adf48b06a2980c9eeffedf699ed5534fade upstream. This patch addresses a null-ptr-deref in qt2_process_read_urb() due to an incorrect bounds check in the following: if (newport > serial->num_ports) { dev_err(&port->dev, "%s - port change to invalid port: %i\n", __func__, newport); break; } The condition doesn't account for the valid range of the serial->port buffer, which is from 0 to serial->num_ports - 1. When newport is equal to serial->num_ports, the assignment of "port" in the following code is out-of-bounds and NULL: serial_priv->current_port = newport; port = serial->port[serial_priv->current_port]; The fix checks if newport is greater than or equal to serial->num_ports indicating it is out-of-bounds. Reported-by: syzbot <syzbot+506479ebf12fe435d01a@syzkaller.appspotmail.com> Closes: https://syzkaller.appspot.com/bug?extid=506479ebf12fe435d01a Fixes: f7a33e608d9a ("USB: serial: add quatech2 usb to serial driver") Cc: <stable@vger.kernel.org> # 3.5 Signed-off-by: Qasim Ijaz <qasdev00@gmail.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Johan Hovold <johan@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ye Bin <yebin10@huawei.com> --- drivers/usb/serial/quatech2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/serial/quatech2.c b/drivers/usb/serial/quatech2.c index 821f25e52ec2..4cde2bd3885f 100644 --- a/drivers/usb/serial/quatech2.c +++ b/drivers/usb/serial/quatech2.c @@ -503,7 +503,7 @@ static void qt2_process_read_urb(struct urb *urb) newport = *(ch + 3); - if (newport > serial->num_ports) { + if (newport >= serial->num_ports) { dev_err(&port->dev, "%s - port change to invalid port: %i\n", __func__, newport); -- 2.34.1