Re: [PATCH v2] serial: qcom-geni: Fix off-by-one error in ida_alloc_range()

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Aug 22, 2025 at 08:05:24PM +0800, Zong Jiang wrote:
> The ida_alloc_range() function expects an inclusive range, meaning both
> the start and end values are valid allocation targets. Passing nr_ports
> as the upper bound allows allocation of an ID equal to nr_ports, which
> is out of bounds when used as an index into the port array.
> 
> Fix this by subtracting 1 from nr_ports in both calls to ida_alloc_range(),
> ensuring the allocated ID stays within the valid range
> [start, nr_ports - 1].
> 
> This prevents potential out-of-bounds access when the allocated ID is used
> as an index.
> 
> Fixes: 9391ab1ed9b3 ("serial: qcom-geni: Make UART port count configurable via Kconfig")
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes: https://lore.kernel.org/r/202508180815.R2nDyajs-lkp@intel.com/
> Signed-off-by: Zong Jiang <quic_zongjian@quicinc.com>
> ---
>  drivers/tty/serial/qcom_geni_serial.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index 9c7b1cea7cfe..0b474d349531 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -271,9 +271,11 @@ static struct qcom_geni_serial_port *get_port_from_line(int line, bool console,
>  		int max_alias_num = of_alias_get_highest_id("serial");
>  
>  		if (line < 0 || line >= nr_ports)
> -			line = ida_alloc_range(&port_ida, max_alias_num + 1, nr_ports, GFP_KERNEL);
> +			line = ida_alloc_range(&port_ida, max_alias_num + 1,
> +					       nr_ports - 1, GFP_KERNEL);
>  		else
> -			line = ida_alloc_range(&port_ida, line, nr_ports, GFP_KERNEL);
> +			line = ida_alloc_range(&port_ida, line,
> +					       nr_ports - 1, GFP_KERNEL);
>  
>  		if (line < 0)
>  			return ERR_PTR(-ENXIO);
> -- 
> 2.34.1
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
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created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
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