RDMA/core: Do not read wild stack memory in uverbs_get_handler_fn()

Sashiko points out the legacy write path in ib_uverbs_write() does
allocate a struct uverbs_attr_bundle, but it doesn't wrap it in a
bundle_priv so downcasting here isn't safe.

Instead lift the method_elm out of the bundle_priv and use it for the
debug function. The legacy write path will leave it set as NULL since the
write method_elm uses a different type.

Cc: stable@vger.kernel.org
Fixes: 1de9287 ("RDMA: Add ib_copy_validate_udata_in()")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>

Author: jgunthorpe

drivers/infiniband/core/ib_core_uverbs.c

@@ -422,12 +422,10 @@ uverbs_api_ioctl_handler_fn uverbs_get_handler_fn(struct ib_udata *udata)
 {
 	struct uverbs_attr_bundle *bundle =
 		rdma_udata_to_uverbs_attr_bundle(udata);
-	struct bundle_priv *pbundle =
-		container_of(&bundle->hdr, struct bundle_priv, bundle);
 
 	lockdep_assert_held(&bundle->ufile->device->disassociate_srcu);
 
-	return srcu_dereference(pbundle->method_elm->handler,
+	return srcu_dereference(bundle->method_elm->handler,
 				&bundle->ufile->device->disassociate_srcu);
 }
 

drivers/infiniband/core/uverbs.h

@@ -244,7 +244,6 @@ struct bundle_priv {
 	size_t internal_used;
 
 	struct radix_tree_root *radix;
-	const struct uverbs_api_ioctl_method *method_elm;
 	void __rcu **radix_slots;
 	unsigned long radix_slots_len;
 	u32 method_key;

drivers/infiniband/core/uverbs_ioctl.c

@@ -397,13 +397,13 @@ static int ib_uverbs_run_method(struct bundle_priv *pbundle,
 	struct uverbs_attr_bundle *bundle =
 		container_of(&pbundle->bundle, struct uverbs_attr_bundle, hdr);
 	size_t uattrs_size = array_size(sizeof(*pbundle->uattrs), num_attrs);
-	unsigned int destroy_bkey = pbundle->method_elm->destroy_bkey;
+	unsigned int destroy_bkey = bundle->method_elm->destroy_bkey;
 	unsigned int i;
 	int ret;
 
 	/* See uverbs_disassociate_api() */
 	handler = srcu_dereference(
-		pbundle->method_elm->handler,
+		bundle->method_elm->handler,
 		&pbundle->bundle.ufile->device->disassociate_srcu);
 	if (!handler)
 		return -EIO;
@@ -421,12 +421,12 @@ static int ib_uverbs_run_method(struct bundle_priv *pbundle,
 	}
 
 	/* User space did not provide all the mandatory attributes */
-	if (unlikely(!bitmap_subset(pbundle->method_elm->attr_mandatory,
+	if (unlikely(!bitmap_subset(bundle->method_elm->attr_mandatory,
 				    pbundle->bundle.attr_present,
-				    pbundle->method_elm->key_bitmap_len)))
+				    bundle->method_elm->key_bitmap_len)))
 		return -EINVAL;
 
-	if (pbundle->method_elm->has_udata)
+	if (bundle->method_elm->has_udata)
 		uverbs_fill_udata(bundle, &pbundle->bundle.driver_udata,
 				  UVERBS_ATTR_UHW_IN, UVERBS_ATTR_UHW_OUT);
 	else
@@ -451,7 +451,7 @@ static int ib_uverbs_run_method(struct bundle_priv *pbundle,
 	 * assume that the driver wrote to its UHW_OUT and flag userspace
 	 * appropriately.
 	 */
-	if (!ret && pbundle->method_elm->has_udata) {
+	if (!ret && bundle->method_elm->has_udata) {
 		const struct uverbs_attr *attr =
 			uverbs_attr_get(bundle, UVERBS_ATTR_UHW_OUT);
 
@@ -472,7 +472,7 @@ static int ib_uverbs_run_method(struct bundle_priv *pbundle,
 
 static void bundle_destroy(struct bundle_priv *pbundle, bool commit)
 {
-	unsigned int key_bitmap_len = pbundle->method_elm->key_bitmap_len;
+	unsigned int key_bitmap_len = pbundle->bundle.method_elm->key_bitmap_len;
 	struct uverbs_attr_bundle *bundle =
 		container_of(&pbundle->bundle, struct uverbs_attr_bundle, hdr);
 	struct bundle_alloc_head *memblock;
@@ -560,7 +560,7 @@ static int ib_uverbs_cmd_verbs(struct ib_uverbs_file *ufile,
 	}
 
 	/* Space for the pbundle->bundle.attrs flex array */
-	pbundle->method_elm = method_elm;
+	pbundle->bundle.method_elm = method_elm;
 	pbundle->method_key = attrs_iter.index;
 	pbundle->bundle.ufile = ufile;
 	pbundle->bundle.context = NULL; /* only valid if bundle has uobject */
@@ -569,10 +569,12 @@ static int ib_uverbs_cmd_verbs(struct ib_uverbs_file *ufile,
 	pbundle->radix_slots_len = radix_tree_chunk_size(&attrs_iter);
 	pbundle->user_attrs = user_attrs;
 
-	pbundle->internal_used = ALIGN(pbundle->method_elm->key_bitmap_len *
-					       sizeof(*container_of(&pbundle->bundle,
-							struct uverbs_attr_bundle, hdr)->attrs),
-					       sizeof(*pbundle->internal_buffer));
+	pbundle->internal_used = ALIGN(
+		pbundle->bundle.method_elm->key_bitmap_len *
+			sizeof(*container_of(&pbundle->bundle,
+					     struct uverbs_attr_bundle, hdr)
+					->attrs),
+		sizeof(*pbundle->internal_buffer));
 	memset(pbundle->bundle.attr_present, 0,
 	       sizeof(pbundle->bundle.attr_present));
 	memset(pbundle->uobj_finalize, 0, sizeof(pbundle->uobj_finalize));

include/rdma/uverbs_ioctl.h

@@ -635,6 +635,7 @@ struct uverbs_attr_bundle {
 		struct ib_uverbs_file *ufile;
 		struct ib_ucontext *context;
 		struct ib_uobject *uobject;
+		const struct uverbs_api_ioctl_method *method_elm;
 		DECLARE_BITMAP(attr_present, UVERBS_API_ATTR_BKEY_LEN);
 	);
 	struct uverbs_attr attrs[];