Re: CVE-2023-52823: kernel: kexec: copy user-array safely

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, May 24, 2024 at 02:38:04PM +0200, Jiri Bohac wrote:
> On Fri, May 24, 2024 at 12:15:47PM +0200, Greg Kroah-Hartman wrote:
> > Nice, but then why was this commit worded this way?  Now we check twice?
> > Double safe?  Should it be reverted?
> 
> double safe's good; turning it into a CVE not so much :(
> CVE-2023-52822, CVE-2023-52824 and CVE-2023-52820, originally from the same patch
> series, seem to be the exact same case.
> 
> CVE-2023-52822:
> 
> 	int vmw_surface_define_ioctl(struct drm_device *dev, void *data,
> 				     struct drm_file *file_priv)
> 	{
> 	...
> 		if (num_sizes > DRM_VMW_MAX_SURFACE_FACES * DRM_VMW_MAX_MIP_LEVELS ||
> 		    num_sizes == 0)
> 			return -EINVAL;
> 	...
> 		metadata->num_sizes = num_sizes;
> 		metadata->sizes =
> 			memdup_user((struct drm_vmw_size __user *)(unsigned long)
> 				    req->size_addr,
> 				    sizeof(*metadata->sizes) * metadata->num_sizes);
> 	}

Agreed, now rejected.

> CVE-2023-52824 (here the check is in the immediately preceeding statement, could it
> be any more obvious?):
> 
> 	long watch_queue_set_filter(struct pipe_inode_info *pipe,
> 				    struct watch_notification_filter __user *_filter)
> 	{
> 		if (filter.nr_filters == 0 ||
> 		    filter.nr_filters > 16 ||
> 		    filter.__reserved != 0)
> 			return -EINVAL;
> 
> 		tf = memdup_user(_filter->filters, filter.nr_filters * sizeof(*tf));
> 	}

Yup, now rejected.

> 
> 
> CVE-2023-52820 is a little less obvious to be safe, but I believe it is:
> 
> 	int drm_mode_create_lease_ioctl(struct drm_device *dev,
> 					void *data, struct drm_file *lessor_priv)
> 	{
> 	...
> 			object_ids = memdup_user(u64_to_user_ptr(cl->object_ids),
> 						 array_size(object_count, sizeof(__u32)));
> 
> 	array_size() will safely multiply object_count * 4 and return SIZE_MAX on
> 	overflow, making the kmalloc inside memdup_user cleanly fail with -ENOMEM.

Also agreed, now rejected.

thanks,

greg k-h

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