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

[Jiri Bohac]

On Tue, May 21, 2024 at 05:31:59PM +0200, Greg Kroah-Hartman wrote:
> kernel: kexec: copy user-array safely
> 
> Currently, there is no overflow-check with memdup_user().

This is false. 
Therefore, I'd like to dispute this CVE.

The overflow check is in the kexec_load_check()
function called shortly before the memdup_user() call:


	SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
			struct kexec_segment __user *, segments, unsigned long, flags)
	{
		result = kexec_load_check(nr_segments, flags);
		if (result)
			return result;
	...
		ksegments = memdup_user(segments, nr_segments * sizeof(ksegments[0]));
	...
	}

	#define KEXEC_SEGMENT_MAX 16
	static inline int kexec_load_check(unsigned long nr_segments,
					   unsigned long flags)
	{
	...
		if (nr_segments > KEXEC_SEGMENT_MAX)
			return -EINVAL;
	}



Thanks,

-- 
Jiri Bohac <jbohac@xxxxxxx>
SUSE Labs, Prague, Czechia