kern/114451: NFS server possible crash

[Rick Macklem]

>Number:         114451
>Category:       kern
>Synopsis:       NFS server possible crash
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Jul 09 17:00:08 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Rick Macklem
>Release:        FreeBSD-CURRENT May snapshot
>Organization:
Univ of Guelph
>Environment:
FreeBSD nfsv4-laptop.cis.uoguelph.ca 7.0-CURRENT-200705 i386
>Description:
Looking at the code, it is pretty obvious that sys/nfsserver/nfs_serv.c would
crash in readdirplus if VFS_VGET() returns an error other than EOPNOTSUPP. See
the "patch" file.
>How-To-Repeat:
Probably doesn't occur in practice, since VFS_VGET() would not normally
return such an error.
>Fix:
See patch file. NB, I haven't actually tested this.

Patch attached with submission follows:

When working on my server port, I spotted the following in FreeBSD-CURRENT
(May 2007 snapshot) in sys/nfsserver/nfs_serv.c (lines 3596-3612)
	/*
	 * Probe one of the directory entries to see if the filesystem
	 * supports VGET.
	 */
	if (VFS_VGET(vp->v_mount, dp->d_fileno, LK_EXCLUSIVE, &nvp) ==
	    EOPNOTSUPP) {
		error = NFSERR_NOTSUPP;
		vrele(vp);
		vp = NULL;
		free((caddr_t)cookies, M_TEMP);
		free((caddr_t)rbuf, M_TEMP);
		nfsm_reply(NFSX_V3POSTOPATTR);
		nfsm_srvpostop_attr(getret, &at);
		error = 0;
		goto nfsmout;
	}
	vput(nvp);
	*** nvp not set when VFS_VGET() returns an error other than
		EOPNOTSUPP.

If you look at the above, it's pretty obvious that, if VFS_VGET() returns
an error other than EOPNOTSUPP, then it vputs crap.
Maybe should be something like (haven't actually tested this):
	/*
	 * Probe one of the directory entries to see if the filesystem
	 * supports VGET.
	 */
	error = VFS_VGET(vp->v_mount, dp->d_fileno, LK_EXCLUSIVE, &nvp);
	if (error == EOPNOTSUPP) {
		error = NFSERR_NOTSUPP;
		vrele(vp);
		vp = NULL;
		free((caddr_t)cookies, M_TEMP);
		free((caddr_t)rbuf, M_TEMP);
		nfsm_reply(NFSX_V3POSTOPATTR);
		nfsm_srvpostop_attr(getret, &at);
		error = 0;
		goto nfsmout;
	}
	if (error)
		error = 0;
	else
		vput(nvp);


>Release-Note:
>Audit-Trail:
>Unformatted: