Re: [PATCH 03/10] scsi: NCR5380: Replace snprintf() with the safer scnprintf() variant

Geert Uytterhoeven
2024-02-08T10:22:45Z

Hi Lee,

Thanks for your patch!

On Thu, Feb 8, 2024 at 9:48 AM Lee Jones <lee@kernel.org> wrote:
> There is a general misunderstanding amongst engineers that {v}snprintf()
> returns the length of the data *actually* encoded into the destination
> array. However, as per the C99 standard {v}snprintf() really returns
> the length of the data that *would have been* written if there were
> enough space for it. This misunderstanding has led to buffer-overruns
> in the past. It's generally considered safer to use the {v}scnprintf()
> variants in their place (or even sprintf() in simple cases). So let's
> do that.

Confused... The return value is not used at all?

> --- a/drivers/scsi/NCR5380.c
> +++ b/drivers/scsi/NCR5380.c
> @@ -421,14 +421,14 @@ static int NCR5380_init(struct Scsi_Host *instance, int flags)
> if (!hostdata->work_q)
> return -ENOMEM;
>
> - snprintf(hostdata->info, sizeof(hostdata->info),
> - "%s, irq %d, io_port 0x%lx, base 0x%lx, can_queue %d, cmd_per_lun %d, sg_tablesize %d, this_id %d, flags { %s%s%s}",
> - instance->hostt->name, instance->irq, hostdata->io_port,
> - hostdata->base, instance->can_queue, instance->cmd_per_lun,
> - instance->sg_tablesize, instance->this_id,
> - hostdata->flags & FLAG_DMA_FIXUP ? "DMA_FIXUP " : "",
> - hostdata->flags & FLAG_NO_PSEUDO_DMA ? "NO_PSEUDO_DMA " : "",
> - hostdata->flags & FLAG_TOSHIBA_DELAY ? "TOSHIBA_DELAY " : "");
> + scnprintf(hostdata->info, sizeof(hostdata->info),
> + "%s, irq %d, io_port 0x%lx, base 0x%lx, can_queue %d, cmd_per_lun %d, sg_tablesize %d, this_id %d, flags { %s%s%s}",
> + instance->hostt->name, instance->irq, hostdata->io_port,
> + hostdata->base, instance->can_queue, instance->cmd_per_lun,
> + instance->sg_tablesize, instance->this_id,
> + hostdata->flags & FLAG_DMA_FIXUP ? "DMA_FIXUP " : "",
> + hostdata->flags & FLAG_NO_PSEUDO_DMA ? "NO_PSEUDO_DMA " : "",
> + hostdata->flags & FLAG_TOSHIBA_DELAY ? "TOSHIBA_DELAY " : "");
>
> NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
> NCR5380_write(MODE_REG, MR_BASE);

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds