On Mon, Jun 03, 2019 at 06:55:14PM +0200, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 kernel ABI to allow to
> pass tagged user pointers (with the top byte set to something else other
> than 0x00) as syscall arguments.
> 
> ib_uverbs_(re)reg_mr() use provided user pointers for vma lookups (through
> e.g. mlx4_get_umem_mr()), which can only by done with untagged pointers.
> 
> Untag user pointers in these functions.
>
> Signed-off-by: Andrey Konovalov <andreyk...@google.com>
>  drivers/infiniband/core/uverbs_cmd.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/infiniband/core/uverbs_cmd.c 
> b/drivers/infiniband/core/uverbs_cmd.c
> index 5a3a1780ceea..f88ee733e617 100644
> +++ b/drivers/infiniband/core/uverbs_cmd.c
> @@ -709,6 +709,8 @@ static int ib_uverbs_reg_mr(struct uverbs_attr_bundle 
> *attrs)
>       if (ret)
>               return ret;
>  
> +     cmd.start = untagged_addr(cmd.start);
> +
>       if ((cmd.start & ~PAGE_MASK) != (cmd.hca_va & ~PAGE_MASK))
>               return -EINVAL;

I feel like we shouldn't thave to do this here, surely the cmd.start
should flow unmodified to get_user_pages, and gup should untag it?

ie, this sort of direction for the IB code (this would be a giant
patch, so I didn't have time to write it all, but I think it is much
saner):

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 54628ef879f0ce..7b3b736c87c253 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -193,7 +193,7 @@ EXPORT_SYMBOL(ib_umem_find_best_pgsz);
  * @access: IB_ACCESS_xxx flags for memory being pinned
  * @dmasync: flush in-flight DMA when the memory region is written
  */
-struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
+struct ib_umem *ib_umem_get(struct ib_udata *udata, void __user *addr,
                            size_t size, int access, int dmasync)
 {
        struct ib_ucontext *context;
@@ -201,7 +201,7 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, 
unsigned long addr,
        struct page **page_list;
        unsigned long lock_limit;
        unsigned long new_pinned;
-       unsigned long cur_base;
+       void __user *cur_base;
        struct mm_struct *mm;
        unsigned long npages;
        int ret;
diff --git a/drivers/infiniband/core/uverbs_cmd.c 
b/drivers/infiniband/core/uverbs_cmd.c
index 5a3a1780ceea4d..94389e7f12371f 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -735,7 +735,8 @@ static int ib_uverbs_reg_mr(struct uverbs_attr_bundle 
*attrs)
                }
        }
 
-       mr = pd->device->ops.reg_user_mr(pd, cmd.start, cmd.length, cmd.hca_va,
+       mr = pd->device->ops.reg_user_mr(pd, u64_to_user_ptr(cmd.start),
+                                        cmd.length, cmd.hca_va,
                                         cmd.access_flags,
                                         &attrs->driver_udata);
        if (IS_ERR(mr)) {
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index 4d033796dcfcc2..bddbb952082fc5 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -786,7 +786,7 @@ static int mr_cache_max_order(struct mlx5_ib_dev *dev)
 }
 
 static int mr_umem_get(struct mlx5_ib_dev *dev, struct ib_udata *udata,
-                      u64 start, u64 length, int access_flags,
+                      void __user *start, u64 length, int access_flags,
                       struct ib_umem **umem, int *npages, int *page_shift,
                       int *ncont, int *order)
 {
@@ -1262,8 +1262,8 @@ struct ib_mr *mlx5_ib_reg_dm_mr(struct ib_pd *pd, struct 
ib_dm *dm,
                                 attr->access_flags, mode);
 }
 
-struct ib_mr *mlx5_ib_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
-                                 u64 virt_addr, int access_flags,
+struct ib_mr *mlx5_ib_reg_user_mr(struct ib_pd *pd, void __user *start,
+                                 u64 length, u64 virt_addr, int access_flags,
                                  struct ib_udata *udata)
 {
        struct mlx5_ib_dev *dev = to_mdev(pd->device);
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index ec6446864b08e9..b3c8eaaa35c760 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -2464,8 +2464,8 @@ struct ib_device_ops {
        struct ib_mr *(*reg_user_mr)(struct ib_pd *pd, u64 start, u64 length,
                                     u64 virt_addr, int mr_access_flags,
                                     struct ib_udata *udata);
-       int (*rereg_user_mr)(struct ib_mr *mr, int flags, u64 start, u64 length,
-                            u64 virt_addr, int mr_access_flags,
+       int (*rereg_user_mr)(struct ib_mr *mr, int flags, void __user *start,
+                            u64 length, u64 virt_addr, int mr_access_flags,
                             struct ib_pd *pd, struct ib_udata *udata);
        int (*dereg_mr)(struct ib_mr *mr, struct ib_udata *udata);
        struct ib_mr *(*alloc_mr)(struct ib_pd *pd, enum ib_mr_type mr_type,
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