kern/61994: panic in linprocfs

[Bjoern Groenvall]

>Number:         61994
>Category:       kern
>Synopsis:       panic in linprocfs
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jan 27 09:40:12 PST 2004
>Closed-Date:
>Last-Modified:
>Originator:     Bjoern Groenvall
>Release:        FreeBSD 5.2-RELEASE i386
>Organization:
SICS
>Environment:
System: FreeBSD filur.sics.se 5.2-RELEASE FreeBSD 5.2-RELEASE #0: Thu Jan 22 22:47:09 CET 2004 root at filur.sics.se:/usr/src/sys/i386/compile/FILUR i386


	
>Description:

When linprocfs is synthesizing the mtab file it does not obey the
rules for proper locking.

>How-To-Repeat:

Mount a number of remote NFS file systems and then perform this
command a number of times.

# cat /compat/linux/proc/mtab

>Fix:

To synthesize the mtab file the following fields are used:

f_mntfromname, f_mntonname, f_fstypename, f_flags

All these fields are available without actually calling VFS_STATFS. If
one still insists on calling VFS_STATFS one should follow the locking
protocol.

--- /usr/src/sys/compat/linprocfs/linprocfs.c.orig	Mon Oct 20 06:10:20 2003
+++ /usr/src/sys/compat/linprocfs/linprocfs.c	Thu Jan 22 21:32:53 2004
@@ -364,9 +364,12 @@
 	mtx_lock(&mountlist_mtx);
 	error = 0;
 	TAILQ_FOREACH(mp, &mountlist, mnt_list) {
+#if 0
+		/* Needs proper locking  but is also superfluous. */
 		error = VFS_STATFS(mp, &mp->mnt_stat, td);
 		if (error)
 			break;
+#endif
 
 		/* determine device name */
 		mntfrom = mp->mnt_stat.f_mntfromname;
>Release-Note:
>Audit-Trail:
>Unformatted: