Subject: Re: linux-next: Tree for Jan 20 -- Kernel panic - Unable to mount root fs

From: Al Viro <[email-masked]>
Date: Tue, 20 Jan 2015 22:50:41 +0000

On Tue, Jan 20, 2015 at 02:13:09PM -0800, Guenter Roeck wrote:

> > > Nuts...  Is reverting just this (do_path_lookup()) part of commit sufficient
> > > to recover the normal behaviour?
> > 
> > Yes.
> > 
> Same on microblaze.

This is completely insane.
static int filename_lookup(int dfd, struct filename *name,
                                unsigned int flags, struct nameidata *nd)
{
        int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd);
        if (unlikely(retval == -ECHILD))
                retval = path_lookupat(dfd, name->name, flags, nd);
        if (unlikely(retval == -ESTALE))
                retval = path_lookupat(dfd, name->name,
                                                flags | LOOKUP_REVAL, nd);

        if (likely(!retval))
                audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
        return retval;
}
doesn't look at _anything_ other than name->name other than for audit_inode().
And name->name is apparently the same.

It looks like something ends up buggering name->name in process, but then
the damn thing appears to be normal after return from filename_lookup()...