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

Thierry Reding
2015-01-21T15:39:17Z

[-- Attachment #1: Type: text/plain, Size: 2522 bytes --]

On Wed, Jan 21, 2015 at 10:24:11AM -0500, Paul Moore wrote:
> On Wednesday, January 21, 2015 03:42:16 PM Thierry Reding wrote:
> > On Wed, Jan 21, 2015 at 12:05:39PM +0100, Sabrina Dubroca wrote:
> > > 2015-01-21, 04:36:38 +0000, Al Viro wrote:
> > > > On Tue, Jan 20, 2015 at 08:01:26PM -0800, Guenter Roeck wrote:
> > > > > With this patch:
> > > > >
> > > > > sys_mkdir .:40775 returned -17
> > > > > sys_mkdir usr:40775 returned 0
> > > > > sys_mkdir usr/lib:40775 returned 0
> > > > > sys_mkdir usr/share:40755 returned 0
> > > > > sys_mkdir usr/share/udhcpc:40755 returned 0
> > > > > sys_mkdir usr/bin:40775 returned 0
> > > > > sys_mkdir usr/sbin:40775 returned 0
> > > > > sys_mkdir mnt:40775 returned 0
> > > > > sys_mkdir proc:40775 returned 0
> > > > > sys_mkdir root:40775 returned 0
> > > > > sys_mkdir lib:40775 returned 0
> > > > > sys_mkdir lib/modules:40775 returned 0
> > > > > ...
> > > > >
> > > > > and the problem is fixed.
> > >
> > > This patch also works for me.
> > >
> > > > ... except that it simply confirms that something's fishy with
> > > > getname_kernel() of ->name of struct filename returned by getname().
> > > > IOW, I still do not understand the mechanism of breakage there.
> > >
> > > I'm not so sure about that. I tried to copy name to a new string in
> > > do_path_lookup and that didn't help.
> > >
> > > Now, I've removed the
> > >
> > > putname(filename);
> > >
> > > line from do_path_lookup and I don't get the panic.
> >
> > That would indicate that somehow the refcount got unbalanced. Looking
> > more closely it seems like the various audit_*() function do take a
> > reference, but maybe that's not enough.
>
> I'm thinking the same thing and I think the problem may be that
> __audit_reusename() is not bumping the filename->refcnt. Can someone who is
> seeing this problem bump the refcnt in __audit_reusename()?
>
> struct filename *
> __audit_reusename(const __user char *uptr)
> {
> struct audit_context *context = current->audit_context;
> struct audit_names *n;
>
> list_for_each_entry(n, &context->names_list, list) {
> if (!n->name)
> continue;
> if (n->name->uptr == uptr) {
> + n->name->refcnt++;
> return n->name;
> }
> }
> return NULL;
> }

That doesn't seem to help, at least in my case.

Thierry

[-- Attachment #2: Type: application/pgp-signature, Size: 819 bytes --]