Re: [PATCH] scsi: fix shift out-of-bounds in sg_build_indirect The num variable is set to 0. The variable num gets its value from scatter_elem_sz. However the minimum value of scatter_elem_sz is PAGE_SHIFT. So setting num to PAGE_SIZE when num < PAGE_SIZE.

[vivek yadav]

Hi Kshitij,

Subject line of your patch should not exceed more than 80 characters
[recommended]
Please check your patch format.

~~vivek

On Mon, Oct 6, 2025 at 11:17 PM Kshitij Paranjape
<kshitijvparanjape@xxxxxxxxx> wrote:
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Reported-by: syzbot+270f1c719ee7baab9941@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=270f1c719ee7baab9941
> Signed-off-by: Kshitij Paranjape <kshitijvparanjape@xxxxxxxxx>
> ---
>  drivers/scsi/sg.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index effb7e768165..9ae41bb256d7 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -1888,6 +1888,7 @@ sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size)
>                 if (num < PAGE_SIZE) {
>                         scatter_elem_sz = PAGE_SIZE;
>                         scatter_elem_sz_prev = PAGE_SIZE;
> +                       num = scatter_elem_sz;
>                 } else
>                         scatter_elem_sz_prev = num;
>         }
> --
> 2.43.0
>
>