Re: [PATCH v9 05/11] scsi: scsi_debug: Report the residual of a write

[Niklas Cassel <cassel@kernel.org>]

On Sun, Sep 27, 2026 at 05:40:39AM +0000, sashiko-bot@kernel.org wrote:
> [Severity: Medium]
> Will this calculation produce an incorrect residual if the command includes
> a very large LBA range?
> 
> In resp_write_scat(), the variables num_by, num, and lb_size are all 32-bit
> integers, and num_by is calculated as:
> 
>     num_by = num * lb_size;
> 
> If num is sufficiently large (e.g., > 8.38M blocks), does this 32-bit
> multiplication overflow and wrap around to a small value?

num_by and sg_off have been u32 since commit 481b5e5c7949 ("scsi: scsi_debug:
add resp_write_scat function").

sg_off (which can already overflow in mainline) is already passed to
do_device_access(), so this is not a new problem...

But sure... I can introduce a prep patch which changes both to u64.


Kind regards,
Niklas