Re: [PATCH] mpt3sas_ctl: fix double-fetch bug in _ctl_ioctl_main()

[Suganath Prabu Subramani]

Please consider this patch as Ack-by: Suganath Prabu S
<suganath-prabu.subramani@xxxxxxxxxxxx>

Thanks,
Suganath.


On Mon, May 27, 2019 at 6:27 AM Gen Zhang <blackgod016574@xxxxxxxxx> wrote:
>
> In _ctl_ioctl_main(), 'ioctl_header' is fetched the first time from
> userspace. 'ioctl_header.ioc_number' is then checked. The legal result
> is saved to 'ioc'. Then, in condition MPT3COMMAND, the whole struct is
> fetched again from the userspace. Then _ctl_do_mpt_command() is called,
> 'ioc' and 'karg' as inputs.
>
> However, a malicious user can change the 'ioc_number' between the two
> fetches, which will cause a potential security issues.  Moreover, a
> malicious user can provide a valid 'ioc_number' to pass the check in
> first fetch, and then modify it in the second fetch.
>
> To fix this, we need to recheck the 'ioc_number' in the second fetch.
>
> Signed-off-by: Gen Zhang <blackgod016574@xxxxxxxxx>
> ---
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_ctl.c b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
> index b2bb47c..5181c03 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_ctl.c
> +++ b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
> @@ -2319,6 +2319,10 @@ _ctl_ioctl_main(struct file *file, unsigned int cmd, void __user *arg,
>                         break;
>                 }
>
> +               if (karg.hdr.ioc_number != ioctl_header.ioc_number) {
> +                       ret = -EINVAL;
> +                       break;
> +               }
>                 if (_IOC_SIZE(cmd) == sizeof(struct mpt3_ioctl_command)) {
>                         uarg = arg;
>                         ret = _ctl_do_mpt_command(ioc, karg, &uarg->mf);