Re: [PATCH v16 12/16] IB, arm64: untag user pointers in ib_uverbs_(re)reg_mr()

[Jason Gunthorpe <jgg@ziepe.ca>]

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 <andreyknvl@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,