[Patch] bug in get_filesystem_info

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Hi,

In get_filesystem_info mnt_sb->s_root of a vfsmntlist entry is directly passed
to d_path without checking whether it is null. This causes a panic in following
situation:

    Process1 is in <filesystem>_put_super. Before this in d_umount, sb->s_root
    is set to null.
    Process2 scans /proc/mounts which enters get_filesystem_info. Since vfsmnt
    entry for the filesystem being unmounted exists, it passes mnt_sb->s_root to
    d_path.

Attached patch fixes that by skipping an entry if sb->s_root is null.

-- 
Amit Kale
Veritas Software ( http://www.veritas.com )
--- linux-2.3.99-pre3/fs/super.c	Tue Mar 28 11:59:08 2000
+++ super.c	Tue Mar 28 13:55:12 2000
@@ -364,6 +364,8 @@ int get_filesystem_info( char *buf )
 	if (!buffer) return 0;
 	for (tmp = vfsmntlist; tmp && len < PAGE_SIZE - 160;
 	    tmp = tmp->mnt_next) {
+		if (!tmp->mnt_sb->s_root)
+			continue;
 		path = d_path(tmp->mnt_sb->s_root, buffer, PAGE_SIZE);
 		if (!path)
 			continue;
-
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