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[34.82.187.25]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-88725881fa6sm376732b3a.27.2026.09.30.00.48.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Sep 2026 00:48:54 -0700 (PDT) From: Hui Peng To: Greg Kroah-Hartman , Jiri Slaby , John Ogness , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Cc: Andy Shevchenko , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Hui Peng Subject: [PATCH v6 3/3] serial: core: reject baud_base values that overflow port->uartclk in uart_set_info() Date: Wed, 30 Sep 2026 07:48:50 +0000 Message-ID: <20260930074850.465003-4-benquike@gmail.com> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog In-Reply-To: <20260930074850.465003-1-benquike@gmail.com> References: <20260930074850.465003-1-benquike@gmail.com> Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In uart_set_info(), new_info->baud_base is multiplied by 16 and stored in uport->uartclk (an unsigned int): uport->uartclk = new_info->baud_base * 16; While uart_set_info() checks if (uartclk == 0), when new_info->baud_base exceeds UINT_MAX / 16 with low bits set (for example, 0x10000001), multiplying by 16 wraps around in 32-bit unsigned arithmetic to a small non-zero value (16), bypassing uartclk == 0 and setting uport->uartclk = 16. Use check_mul_overflow(new_info->baud_base, 16, &uartclk) in uart_set_info() to reject baud_base values that overflow 32-bit unsigned arithmetic. Tested in QEMU against Linux 7.3.0-rc3 by calling ioctl(fd, TIOCSSERIAL, &ss) with ss.baud_base = 0x10000001 on /dev/ttyS1: on the unfixed kernel TIOCSSERIAL succeeds (ret = 0) and wraps uport->uartclk to 16 (TIOCGSERIAL reports baud_base = 1), whereas with the fix applied TIOCSSERIAL returns -EINVAL and preserves the existing uport->uartclk. Fixes: 6eabce6608d6 ("serial: core: check uartclk for zero to avoid divide by zero") Cc: stable@vger.kernel.org Reviewed-by: Ilpo Järvinen Assisted-by: LLM Signed-off-by: Hui Peng --- Changes in v6: - Use check_mul_overflow() as suggested by Jiri Slaby. Changes in v5: - Collect Reviewed-by from Ilpo Järvinen. drivers/tty/serial/serial_core.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 95774b0f1484..75bb1eaa27e7 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -935,11 +935,6 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port, unsigned int uartclk; /* check needs to be done here before other settings made */ - if (new_info->baud_base > UINT_MAX / 16) - return -EINVAL; - - uartclk = new_info->baud_base * 16; - if (uartclk == 0) + if (check_mul_overflow(new_info->baud_base, 16, &uartclk) || !uartclk) return -EINVAL; } -- 2.47.3