kern/60645: nfssvc(2): arithmetic overflow in input array sizing

["campbell+netbsd%mumble.net@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60645
>Category:       kern
>Synopsis:       nfssvc(2): arithmetic overflow in input array sizing
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Aug 26 02:10:00 +0000 2026
>Originator:     Taylor R Campbell
>Release:        current, 11, 10, 9, ...
>Organization:
The NetBSD Filexportation, In)3^=$,*%928:5%-%76)0
>Environment:
>Description:

	Unchecked multiplication for an array malloc can lead to
	overflow and various downstream consequences:

    343 	} else if (flag & (NFSSVC_SETEXPORTSLIST | NFSSVC_REPLACEEXPORTSLIST)) {
    344 		struct export_args *args;
    345 		struct mountd_exports_list mel;
    346 
    347 		error = ops->setexports_in(&mel, argp);
    348 		if (error != 0)
    349 			return error;
    350 
    351 		args = (struct export_args *)malloc(mel.mel_nexports *
    352 		    sizeof(struct export_args), M_TEMP, M_WAITOK);
    353 		error = ops->exp_in(args, mel.mel_exports, mel.mel_nexports);

	https://nxr.netbsd.org/xref/src/sys/nfs/nfs_syscalls.c?r=1.165#343

>How-To-Repeat:

	code inspection

	export a file system too many different ways

>Fix:

	set a maximum number of exports per mount point