drm/amdgpu: Fix integer overflow issues in amdgpu_userq_fence.c

This patch only affects 32bit systems. There are several integer
overflows bugs here but only the "sizeof(u32) * num_syncobj"
multiplication is a problem at runtime. (The last lines of this patch).

These variables are u32 variables that come from the user. The issue
is the multiplications can overflow leading to us allocating a smaller
buffer than intended. For the first couple integer overflows, the
syncobj_handles = memdup_user() allocation is immediately followed by
a kmalloc_array():

syncobj = kmalloc_array(num_syncobj_handles, sizeof(*syncobj), GFP_KERNEL);

In that situation the kmalloc_array() works as a bounds check and we
haven't accessed the syncobj_handlesp[] array yet so the integer overflow
is harmless.

But the "num_syncobj" multiplication doesn't have that and the integer
overflow could lead to an out of bounds access.

Fixes: a292fdecd728 ("drm/amdgpu: Implement userqueue signal/wait IOCTL")
Signed-off-by: Dan Carpenter <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c

···
 
 	num_syncobj_handles = args->num_syncobj_handles;
 	syncobj_handles = memdup_user(u64_to_user_ptr(args->syncobj_handles),
-				      sizeof(u32) * num_syncobj_handles);
+				      size_mul(sizeof(u32), num_syncobj_handles));
 	if (IS_ERR(syncobj_handles))
 		return PTR_ERR(syncobj_handles);
 
···
 
 	num_read_bo_handles = wait_info->num_bo_read_handles;
 	bo_handles_read = memdup_user(u64_to_user_ptr(wait_info->bo_read_handles),
-				      sizeof(u32) * num_read_bo_handles);
+				      size_mul(sizeof(u32), num_read_bo_handles));
 	if (IS_ERR(bo_handles_read))
 		return PTR_ERR(bo_handles_read);
 
 	num_write_bo_handles = wait_info->num_bo_write_handles;
 	bo_handles_write = memdup_user(u64_to_user_ptr(wait_info->bo_write_handles),
-				       sizeof(u32) * num_write_bo_handles);
+				       size_mul(sizeof(u32), num_write_bo_handles));
 	if (IS_ERR(bo_handles_write)) {
 		r = PTR_ERR(bo_handles_write);
 		goto free_bo_handles_read;
···
 
 	num_syncobj = wait_info->num_syncobj_handles;
 	syncobj_handles = memdup_user(u64_to_user_ptr(wait_info->syncobj_handles),
-				      sizeof(u32) * num_syncobj);
+				      size_mul(sizeof(u32), num_syncobj));
 	if (IS_ERR(syncobj_handles)) {
 		r = PTR_ERR(syncobj_handles);
 		goto free_bo_handles_write;