On Thu, Feb 08, 2024 at 08:44:18AM +0000, Lee Jones 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.
It may be better to do a global replace of snprintf() where the return
value is not used.
$ git grep '\bsnprintf\b' | grep -v = | wc -l
6400
There's plenty of work to do to remove just the ones taking the result:
$ git grep ' = snprintf\b' | wc -l
764
Regardless,
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
-Kees
>
> Link: https://lwn.net/Articles/69419/
> Link: https://github.com/KSPP/linux/issues/105
> Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
> ---
> Cc: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxx>
> Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
> Cc: linux-scsi@xxxxxxxxxxxxxxx
> ---
> drivers/scsi/aha1542.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/aha1542.c b/drivers/scsi/aha1542.c
> index 9503996c63256..b5ec7887801a5 100644
> --- a/drivers/scsi/aha1542.c
> +++ b/drivers/scsi/aha1542.c
> @@ -772,7 +772,7 @@ static struct Scsi_Host *aha1542_hw_init(const struct scsi_host_template *tpnt,
> goto unregister;
>
> if (sh->dma_channel != 0xFF)
> - snprintf(dma_info, sizeof(dma_info), "DMA %d", sh->dma_channel);
> + scnprintf(dma_info, sizeof(dma_info), "DMA %d", sh->dma_channel);
> shost_printk(KERN_INFO, sh, "Adaptec AHA-1542 (SCSI-ID %d) at IO 0x%x, IRQ %d, %s\n",
> sh->this_id, base_io, sh->irq, dma_info);
> if (aha1542->bios_translation == BIOS_TRANSLATION_25563)
> --
> 2.43.0.594.gd9cf4e227d-goog
>
>
--
Kees Cook
