On Wed, 21 Feb 2018 12:22:08 +0000
Shameer Kolothum <shameerali.kolothum.th...@huawei.com> wrote:

> This  allows the user-space to retrieve the supported IOVA
> range(s), excluding any reserved regions. The implementation
> is based on capability chains, added to VFIO_IOMMU_GET_INFO ioctl.
> 
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.th...@huawei.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 88 
> +++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       | 23 +++++++++++
>  2 files changed, 111 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 3049393..c08adb5 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1917,6 +1917,68 @@ static int vfio_domains_have_iommu_cache(struct 
> vfio_iommu *iommu)
>       return ret;
>  }
>  
> +static int vfio_iommu_iova_add_cap(struct vfio_info_cap *caps,
> +              struct vfio_iommu_type1_info_cap_iova_range *cap_iovas,
> +              size_t size)
> +{
> +     struct vfio_info_cap_header *header;
> +     struct vfio_iommu_type1_info_cap_iova_range *iova_cap;
> +
> +     header = vfio_info_cap_add(caps, size,
> +                             VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE, 1);
> +     if (IS_ERR(header))
> +             return PTR_ERR(header);
> +
> +     iova_cap = container_of(header,
> +                     struct vfio_iommu_type1_info_cap_iova_range, header);
> +     iova_cap->nr_iovas = cap_iovas->nr_iovas;
> +     memcpy(iova_cap->iova_ranges, cap_iovas->iova_ranges,
> +             cap_iovas->nr_iovas * sizeof(*cap_iovas->iova_ranges));
> +     return 0;
> +}
> +
> +static int vfio_iommu_iova_build_caps(struct vfio_iommu *iommu,
> +                             struct vfio_info_cap *caps)
> +{
> +     struct vfio_iommu_type1_info_cap_iova_range *cap_iovas;
> +     struct vfio_iova *iova;
> +     size_t size;
> +     int iovas = 0, i = 0, ret;
> +
> +     mutex_lock(&iommu->lock);
> +
> +     list_for_each_entry(iova, &iommu->iova_list, list)
> +             iovas++;
> +
> +     if (!iovas) {
> +             ret = -EINVAL;
> +             goto out_unlock;
> +     }
> +
> +     size = sizeof(*cap_iovas) + (iovas * sizeof(*cap_iovas->iova_ranges));
> +
> +     cap_iovas = kzalloc(size, GFP_KERNEL);
> +     if (!cap_iovas) {
> +             ret = -ENOMEM;
> +             goto out_unlock;
> +     }
> +
> +     cap_iovas->nr_iovas = iovas;
> +
> +     list_for_each_entry(iova, &iommu->iova_list, list) {
> +             cap_iovas->iova_ranges[i].start = iova->start;
> +             cap_iovas->iova_ranges[i].end = iova->end;
> +             i++;
> +     }
> +
> +     ret = vfio_iommu_iova_add_cap(caps, cap_iovas, size);
> +
> +     kfree(cap_iovas);
> +out_unlock:
> +     mutex_unlock(&iommu->lock);
> +     return ret;
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>                                  unsigned int cmd, unsigned long arg)
>  {
> @@ -1938,6 +2000,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>               }
>       } else if (cmd == VFIO_IOMMU_GET_INFO) {
>               struct vfio_iommu_type1_info info;
> +             struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
> +             int ret;
>  
>               minsz = offsetofend(struct vfio_iommu_type1_info, iova_pgsizes);
>  
> @@ -1951,6 +2015,30 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  
>               info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
>  
> +             ret = vfio_iommu_iova_build_caps(iommu, &caps);
> +             if (ret)
> +                     return ret;
> +
> +             if (caps.size) {
> +                     info.flags |= VFIO_IOMMU_INFO_CAPS;
> +
> +                     if (info.argsz < sizeof(info) + caps.size) {
> +                             info.argsz = sizeof(info) + caps.size;

There's still a corner case here where the user could have provided an
argsz including cap_offset, potentially including uninitialized user
data, and it becomes more error prone not to zero that field for this
case.  I'd suggest this:

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index a1ce8853caf1..d9ea69e62c46 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2105,16 +2105,25 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
        } else if (cmd == VFIO_IOMMU_GET_INFO) {
                struct vfio_iommu_type1_info info;
                struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
+               unsigned long capsz;
                int ret;
 
                minsz = offsetofend(struct vfio_iommu_type1_info, iova_pgsizes);
 
+               /* For backward compatibility, cannot require this */
+               capsz = offsetofend(struct vfio_iommu_type1_info, cap_offset);
+
                if (copy_from_user(&info, (void __user *)arg, minsz))
                        return -EFAULT;
 
                if (info.argsz < minsz)
                        return -EINVAL;
 
+               if (info.argsz >= capsz) {
+                       minsz = capsz;
+                       info.cap_offset = 0; /* output, no-recopy necessary */
+               }
+
                info.flags = VFIO_IOMMU_INFO_PGSIZES;
 
                info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
@@ -2136,13 +2145,12 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
                                        kfree(caps.buf);
                                        return -EFAULT;
                                }
-                               minsz = offsetofend(struct 
vfio_iommu_type1_info,
-                                                          cap_offset);
                                info.cap_offset = sizeof(info);
                        }
 
                        kfree(caps.buf);
                }
+
                return copy_to_user((void __user *)arg, &info, minsz) ?
                        -EFAULT : 0;
 


If you approve and there are no other comments, I can roll that change
into this patch as-is.  Thanks,

Alex

> +                     } else {
> +                             vfio_info_cap_shift(&caps, sizeof(info));
> +                             if (copy_to_user((void __user *)arg +
> +                                             sizeof(info), caps.buf,
> +                                             caps.size)) {
> +                                     kfree(caps.buf);
> +                                     return -EFAULT;
> +                             }
> +                             minsz = offsetofend(struct 
> vfio_iommu_type1_info,
> +                                                        cap_offset);
> +                             info.cap_offset = sizeof(info);
> +                     }
> +
> +                     kfree(caps.buf);
> +             }
>               return copy_to_user((void __user *)arg, &info, minsz) ?
>                       -EFAULT : 0;
>  
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index c743721..46b49e9 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -589,7 +589,30 @@ struct vfio_iommu_type1_info {
>       __u32   argsz;
>       __u32   flags;
>  #define VFIO_IOMMU_INFO_PGSIZES (1 << 0)     /* supported page sizes info */
> +#define VFIO_IOMMU_INFO_CAPS (1 << 1)        /* Info supports caps */
>       __u64   iova_pgsizes;           /* Bitmap of supported page sizes */
> +     __u32   cap_offset;     /* Offset within info struct of first cap */
> +};
> +
> +/*
> + * The IOVA capability allows to report the valid IOVA range(s)
> + * excluding any reserved regions associated with dev group. Any dma
> + * map attempt outside the valid iova range will return error.
> + *
> + * The structures below define version 1 of this capability.
> + */
> +#define VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE  1
> +
> +struct vfio_iova_range {
> +     __u64   start;
> +     __u64   end;
> +};
> +
> +struct vfio_iommu_type1_info_cap_iova_range {
> +     struct vfio_info_cap_header header;
> +     __u32   nr_iovas;
> +     __u32   reserved;
> +     struct vfio_iova_range iova_ranges[];
>  };
>  
>  #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)

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