Re: [2.5.36] oops when reading /proc/locks

From: Matthew Wilcox (
Date: Thu Sep 19 2002 - 15:16:23 EST

[note: please cc me or linux-fsdevel when reporting file locking bugs;
i only read linux-kernel on the web and as time permits]

It looks to me like your dereference comes from this line:

        if (fl->fl_file != NULL)
                inode = fl->fl_file->f_dentry->d_inode;

and, if my terribly weak x86 assembler isn't deceiving me, f_dentry
is NULL. Since you can reproduce this at will, could you insert some
debugging for me?

        if (fl->fl_file != NULL) {
                if (fl->fl_file->f_dentry) {
                        inode = fl->fl_file->f_dentry->d_inode;
                } else {
                        printk(KERN_EMERG "null dentry at %d\n", id);

That will avoid the oops, and tell us who managed to set a file lock on
a file without a dentry.

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