On 24.08.2022 16:26, Juergen Gross wrote:
> The error exit of privcmd_ioctl_dm_op() is calling unlock_pages()
> potentially with pages being NULL, leading to a NULL dereference.
>
> Fix that by calling unlock_pages only if lock_pages() was at least
> partially successful.
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP")
> Reported-by: Rustam Subkhankulov <subkhankulov@xxxxxxxxx>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
albeit I wonder whether you did consider the variant actually
reducing code size (and avoiding the need for yet another label),
...
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -679,7 +679,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
> rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned);
> if (rc < 0) {
> nr_pages = pinned;
... dropping this line and ...
> - goto out;
> + goto unlock;
> }
>
> for (i = 0; i < kdata.num; i++) {
> @@ -691,8 +691,9 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
> rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
> xen_preemptible_hcall_end();
>
> -out:
> + unlock:
> unlock_pages(pages, nr_pages);
... passing "pinned" here.
Jan
> + out:
> kfree(xbufs);
> kfree(pages);
> kfree(kbufs);
