Oops on umount -a -f

[Frank Cornelis]

Hi,

This Oops has been annoying me for a while now so here's the report after
some disassembling.
Situation: linux 2.4.19 rh7.3 when I poweroff and the system is doing
	umount -a -f

In the file:function fs/file_table.c:fs_may_remount_ro
	struct inode *inode = file->f_dentry->d_inode;
oopses (NULL ptr deref at 00000008) on instruction fs_may_remount_ro+19:
	0xc0138550 <fs_may_remount_ro+16>:      mov    0x8(%edx),%eax
	0xc0138553 <fs_may_remount_ro+19>:      mov    0x8(%eax),%eax
which does the evaluation of
        f_dentry->d_inode
so seems like file->f_dentry can be NULL, which should be checked first.

A quick and dirty patch for this:
--- fs/file_table.c.orig-2.4.19 Tue Sep 24 11:58:17 2002
+++ fs/file_table.c     Tue Sep 24 12:00:34 2002
@@ -170,7 +170,11 @@
        file_list_lock();
        for (p = sb->s_files.next; p != &sb->s_files; p = p->next) {
                struct file *file = list_entry(p, struct file, f_list);
-               struct inode *inode = file->f_dentry->d_inode;
+               struct dentry *dentry = file->f_dentry;
+               struct inode *inode;
+               if (!dentry)
+                 continue;
+               inode = dentry->d_inode;

                /* File with pending delete? */
                if (inode->i_nlink == 0)

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Greetz,
Frank.