Re: [uml-devel] current_thread_info() returns invalid pointer in early UML boot code

[Thomas M. <th...@m3...>]

Hi,

Mhh. Strange. Do you have a stack trace to call to current thread info which ends up with a wrong value. I wonder from were it originates.

With kind regards 
Thomas


With kind regards
Thomas

> Am 21.05.2016 um 15:51 schrieb Vegard Nossum <veg...@gm...>:
> 
> Hi people,
> 
> I'm having some trouble with using current_thread_info() during UML
> early boot. Sometimes it works just fine, but often I get segfaults
> because current_thread_info() is returning an invalid pointer. It
> looks random: 0x202118, 0x1003e0003, 0xd33b90b3, 0x6db043, etc.
> 
> I found an earlier thread which described the same problem:
> http://permalink.gmane.org/gmane.linux.uml.devel/14642
> 
> However, I think the patch there is a bit hacky/papers over an
> underlying bug, since it just uses is_kernel_addr() before deciding
> whether to return the pointer from current_thread_info() or not. The
> fact that the crash is random leads me to think it's some sort of race
> during the UML boot.
> 
> Does anybody understand fully what's going on here, why it returns
> those invalid (seemingly random) values? If the problem is that we're
> on a wrong stack, can we switch stacks earlier during boot or
> something to make current_thread_info() always return a valid
> thread_info pointer?
> 
> Thanks,
> 
> 
> Vegard
> 
> ------------------------------------------------------------------------------
> Mobile security can be enabling, not merely restricting. Employees who
> bring their own devices (BYOD) to work are irked by the imposition of MDM
> restrictions. Mobile Device Manager Plus allows you to control only the
> apps on BYO-devices by containerizing them, leaving personal data untouched!
> https://ad.doubleclick.net/ddm/clk/304595813;131938128;j
> _______________________________________________
> User-mode-linux-devel mailing list
> Use...@li...
> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel