Re: [PATCH] scsi/lsi53c895a: fix use-after-free in lsi_do_msgout (CVE-2022-0216)

[Thomas Huth]

On 05/07/2022 22.05, Mauro Matteo Cascella wrote:
> Set current_req->req to NULL to prevent reusing a free'd buffer in case of
> repeated SCSI cancel requests. Thanks to Thomas Huth for suggesting the patch.
>
> Fixes: CVE-2022-0216
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/972
> Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
> ---
>   hw/scsi/lsi53c895a.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
> index c8773f73f7..99ea42d49b 100644
> --- a/hw/scsi/lsi53c895a.c
> +++ b/hw/scsi/lsi53c895a.c
> @@ -1028,8 +1028,9 @@ static void lsi_do_msgout(LSIState *s)
>           case 0x0d:
>               /* The ABORT TAG message clears the current I/O process only. */
>               trace_lsi_do_msgout_abort(current_tag);
> -            if (current_req) {
> +            if (current_req && current_req->req) {
>                   scsi_req_cancel(current_req->req);
> +                current_req->req = NULL;
>               }
>               lsi_disconnect(s);
>               break;

Let's hope that this will fix the issue for good...

Reviewed-by: Thomas Huth <thuth@redhat.com>