Re: [Xen-devel] [PATCH V3] Correctly return success from IOCTL_PRIVCMD_MMAPBATCH

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 16/11/12 18:36, Mats Petersson wrote:
> This is a regression introduced by ceb90fa0 (xen/privcmd: add
> PRIVCMD_MMAPBATCH_V2 ioctl).  It broke xentrace as it used
> xc_map_foreign() instead of xc_map_foreign_bulk().

Konrad,

This is a regression introduced in 3.7-rc1.  Can you pick this one up
for 3.7?  Thanks.

David

> 
> Most code-paths prefer the MMAPBATCH_V2, so this wasn't very obvious
> that it broke. The return value is set early on to -EINVAL, and if all
> goes well, the "set top bits of the MFN's" never gets called, so the
> return value is still EINVAL when the function gets to the end, causing
> the caller to think it went wrong (which it didn't!)
> 
> Now also including Andres "move the ret = -EINVAL into the error handling 
> path, as this avoids other similar errors in future.
> 
> Signed off by: Mats Petersson <mats.petersson@xxxxxxxxxx>
> Acked-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
> Acked-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
>  drivers/xen/privcmd.c |   18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index 8adb9cc..71f5c45 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -361,13 +361,13 @@ static long privcmd_ioctl_mmap_batch(void __user 
> *udata, int version)
>       down_write(&mm->mmap_sem);
>  
>       vma = find_vma(mm, m.addr);
> -     ret = -EINVAL;
>       if (!vma ||
>           vma->vm_ops != &privcmd_vm_ops ||
>           (m.addr != vma->vm_start) ||
>           ((m.addr + (nr_pages << PAGE_SHIFT)) != vma->vm_end) ||
>           !privcmd_enforce_singleshot_mapping(vma)) {
>               up_write(&mm->mmap_sem);
> +             ret = -EINVAL;
>               goto out;
>       }
>  
> @@ -383,12 +383,16 @@ static long privcmd_ioctl_mmap_batch(void __user 
> *udata, int version)
>  
>       up_write(&mm->mmap_sem);
>  
> -     if (state.global_error && (version == 1)) {
> -             /* Write back errors in second pass. */
> -             state.user_mfn = (xen_pfn_t *)m.arr;
> -             state.err      = err_array;
> -             ret = traverse_pages(m.num, sizeof(xen_pfn_t),
> -                                  &pagelist, mmap_return_errors_v1, &state);
> +     if (version == 1) {
> +             if (state.global_error) {
> +                     /* Write back errors in second pass. */
> +                     state.user_mfn = (xen_pfn_t *)m.arr;
> +                     state.err      = err_array;
> +                     ret = traverse_pages(m.num, sizeof(xen_pfn_t),
> +                                          &pagelist, mmap_return_errors_v1, 
> &state);
> +             } else
> +                     ret = 0;
> +
>       } else if (version == 2) {
>               ret = __copy_to_user(m.err, err_array, m.num * sizeof(int));
>               if (ret)


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