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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 01/21/2015 07:54 AM, Sabrina Dubroca wrote:
2015-01-21, 16:39:12 +0100, Thierry Reding wrote:
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.

Same here.

Well, it's probably not an audit issue.  I tried audit=0 on the
commandline, and I just rebuilt a kernel with CONFIG_AUDIT=n, and it's
still panicing.  This should have fixed any audit-related issue,
right?

I don't have audit enabled, so I don't think that is the problem either
(the refcount increase didn't help, and a WARN(1) added to the code
at the same location did not trigger).

Wonder if we have a use-after-free case and just have been lucky all along.

Guenter

--
To unsubscribe from this list: send the line "unsubscribe linux-next" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Kernel]     [Linux USB Development]     [Yosemite News]     [Linux SCSI]

  Powered by Linux