IB/uverbs: Handle IDR and FD types without truncation

Our ABI for write() uses a s32 for FDs and a u32 for IDRs, but internally
we ended up implicitly casting these ABI values into an 'int'. For ioctl()
we use a s64 for FDs and a u64 for IDRs, again casting to an int.

The various casts to int are all missing range checks which can cause
userspace values that should be considered invalid to be accepted.

Fix this by making the generic lookup routine accept a s64, which does not
truncate the write API's u32/s32 or the ioctl API's s64. Then push the
detailed range checking down to the actual type implementations to be
shared by both interfaces.

Finally, change the copy of the uobj->id to sign extend into a s64, so eg,
if we ever wish to return a negative value for a FD it is carried
properly.

This ensures that userspace values are never weirdly interpreted due to
the various trunctations and everything that is really out of range gets
an EINVAL.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

4 files changed, 30 insertions, 18 deletions

diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c
index aed7cc2a9e86..c63583dbc6b9 100644
--- a/drivers/infiniband/core/rdma_core.c
+++ b/drivers/infiniband/core/rdma_core.c
@@ -133,7 +133,7 @@ static int uverbs_try_lock_object(struct ib_uobject *uobj, bool exclusive)
  * returns success_res on success (negative errno on failure). For use by
  * callers that do not need the uobj.
  */
-int __uobj_perform_destroy(const struct uverbs_obj_type *type, int id,
+int __uobj_perform_destroy(const struct uverbs_obj_type *type, u32 id,
 			   struct ib_uverbs_file *ufile, int success_res)
 {
 	struct ib_uobject *uobj;
@@ -212,13 +212,17 @@ static void uverbs_idr_remove_uobj(struct ib_uobject *uobj)
 /* Returns the ib_uobject or an error. The caller should check for IS_ERR. */
 static struct ib_uobject *
 lookup_get_idr_uobject(const struct uverbs_obj_type *type,
-		       struct ib_uverbs_file *ufile, int id, bool exclusive)
+		       struct ib_uverbs_file *ufile, s64 id, bool exclusive)
 {
 	struct ib_uobject *uobj;
+	unsigned long idrno = id;
+
+	if (id < 0 || id > ULONG_MAX)
+		return ERR_PTR(-EINVAL);
 
 	rcu_read_lock();
 	/* object won't be released as we're protected in rcu */
-	uobj = idr_find(&ufile->idr, id);
+	uobj = idr_find(&ufile->idr, idrno);
 	if (!uobj) {
 		uobj = ERR_PTR(-ENOENT);
 		goto free;
@@ -240,17 +244,21 @@ free:
 
 static struct ib_uobject *lookup_get_fd_uobject(const struct uverbs_obj_type *type,
 						struct ib_uverbs_file *ufile,
-						int id, bool exclusive)
+						s64 id, bool exclusive)
 {
 	struct file *f;
 	struct ib_uobject *uobject;
+	int fdno = id;
 	const struct uverbs_obj_fd_type *fd_type =
 		container_of(type, struct uverbs_obj_fd_type, type);
 
+	if (fdno != id)
+		return ERR_PTR(-EINVAL);
+
 	if (exclusive)
 		return ERR_PTR(-EOPNOTSUPP);
 
-	f = fget(id);
+	f = fget(fdno);
 	if (!f)
 		return ERR_PTR(-EBADF);
 
@@ -270,7 +278,7 @@ static struct ib_uobject *lookup_get_fd_uobject(const struct uverbs_obj_type *ty
 }
 
 struct ib_uobject *rdma_lookup_get_uobject(const struct uverbs_obj_type *type,
-					   struct ib_uverbs_file *ufile, int id,
+					   struct ib_uverbs_file *ufile, s64 id,
 					   bool exclusive)
 {
 	struct ib_uobject *uobj;
@@ -725,7 +733,7 @@ EXPORT_SYMBOL(uverbs_fd_class);
 struct ib_uobject *
 uverbs_get_uobject_from_file(const struct uverbs_obj_type *type_attrs,
 			     struct ib_uverbs_file *ufile,
-			     enum uverbs_obj_access access, int id)
+			     enum uverbs_obj_access access, s64 id)
 {
 	switch (access) {
 	case UVERBS_ACCESS_READ:
diff --git a/drivers/infiniband/core/rdma_core.h b/drivers/infiniband/core/rdma_core.h
index 1bba60e960c1..db2339330f6f 100644
--- a/drivers/infiniband/core/rdma_core.h
+++ b/drivers/infiniband/core/rdma_core.h
@@ -86,7 +86,7 @@ void uverbs_close_fd(struct file *f);
 struct ib_uobject *
 uverbs_get_uobject_from_file(const struct uverbs_obj_type *type_attrs,
 			     struct ib_uverbs_file *ufile,
-			     enum uverbs_obj_access access, int id);
+			     enum uverbs_obj_access access, s64 id);
 
 /*
  * Note that certain finalize stages could return a status:
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 987ee38ab4b3..409fd46a2a99 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -48,10 +48,10 @@
 #include "core_priv.h"
 
 static struct ib_uverbs_completion_event_file *
-ib_uverbs_lookup_comp_file(int fd, struct ib_uverbs_file *ufile)
+_ib_uverbs_lookup_comp_file(s32 fd, struct ib_uverbs_file *ufile)
 {
-	struct ib_uobject *uobj = uobj_get_read(UVERBS_OBJECT_COMP_CHANNEL,
-						fd, ufile);
+	struct ib_uobject *uobj = ufd_get_read(UVERBS_OBJECT_COMP_CHANNEL,
+					       fd, ufile);
 
 	if (IS_ERR(uobj))
 		return (void *)uobj;
@@ -62,6 +62,8 @@ ib_uverbs_lookup_comp_file(int fd, struct ib_uverbs_file *ufile)
 	return container_of(uobj, struct ib_uverbs_completion_event_file,
 			    uobj);
 }
+#define ib_uverbs_lookup_comp_file(_fd, _ufile)                                \
+	_ib_uverbs_lookup_comp_file((_fd)*typecheck(s32, _fd), _ufile)
 
 ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 			      struct ib_device *ib_dev,
diff --git a/drivers/infiniband/core/uverbs_ioctl.c b/drivers/infiniband/core/uverbs_ioctl.c
index d3bf82cfaa2b..26ddc5cadcdb 100644
--- a/drivers/infiniband/core/uverbs_ioctl.c
+++ b/drivers/infiniband/core/uverbs_ioctl.c
@@ -136,15 +136,11 @@ static int uverbs_process_attr(struct ib_uverbs_file *ufile,
 		break;
 
 	case UVERBS_ATTR_TYPE_IDR:
-		if (uattr->data >> 32)
-			return -EINVAL;
-	/* fall through */
 	case UVERBS_ATTR_TYPE_FD:
 		if (uattr->attr_data.reserved)
 			return -EINVAL;
 
-		if (uattr->len != 0 || !ufile->ucontext ||
-		    uattr->data > INT_MAX)
+		if (uattr->len != 0 || !ufile->ucontext)
 			return -EINVAL;
 
 		o_attr = &e->obj_attr;
@@ -152,17 +148,23 @@ static int uverbs_process_attr(struct ib_uverbs_file *ufile,
 		if (!object)
 			return -EINVAL;
 
+		/*
+		 * The type of uattr->data is u64 for UVERBS_ATTR_TYPE_IDR and
+		 * s64 for UVERBS_ATTR_TYPE_FD. We can cast the u64 to s64
+		 * here without caring about truncation as we know that the
+		 * IDR implementation today rejects negative IDs
+		 */
 		o_attr->uobject = uverbs_get_uobject_from_file(
 					object->type_attrs,
 					ufile,
 					spec->u.obj.access,
-					(int)uattr->data);
+					uattr->data_s64);
 
 		if (IS_ERR(o_attr->uobject))
 			return PTR_ERR(o_attr->uobject);
 
 		if (spec->u.obj.access == UVERBS_ACCESS_NEW) {
-			u64 id = o_attr->uobject->id;
+			s64 id = o_attr->uobject->id;
 
 			/* Copy the allocated id to the user-space */
 			if (put_user(id, &e->uattr->data)) {