Re: [PATCH] ppdev: fix double-free of pp->pdev->name

Greg Kroah-Hartman
2016-10-30T22:12:25Z

On Sun, Oct 30, 2016 at 07:00:36PM +0100, Jann Horn wrote:
> On Sun, Oct 30, 2016 at 11:24:27PM +0530, Sudip Mukherjee wrote:
> > On Sunday 30 October 2016 09:14 PM, Jann Horn wrote:
> > >free_pardevice() is called by parport_unregister_device() and already frees
> > >pp->pdev->name, don't try to do it again.
> > >
> > >This bug causes kernel crashes.
> > >
> > >I found and verified this with KASAN and some added pr_emerg()s:
> > >
> > >[ 60.316568] pp_release: pp->pdev->name == ffff88039cb264c0
> > >[ 60.316692] free_pardevice: freeing par_dev->name at ffff88039cb264c0
> > >[ 60.316706] pp_release: kfree(ffff88039cb264c0)
> > >[ 60.316714] ==========================================================
> > >[ 60.316722] BUG: Double free or freeing an invalid pointer
> > >[ 60.316731] Unexpected shadow byte: 0xFB
> > >[ 60.316801] Object at ffff88039cb264c0, in cache kmalloc-32 size: 32
> > >[ 60.316813] Allocated:
> > >[ 60.316824] PID = 1695
> > >[ 60.316869] Freed:
> > >[ 60.316880] PID = 1695
> > >[ 60.316935] ==========================================================
> > >
> > >CCing Andy Lutomirski because I think this is what broke vmapped stacks
> > >for me - after applying this patch, vmapped stacks worked for me.
> > >Previously, I got oopses (and lockups) caused by area->pages[0] being
> > >0x400000000 in __vunmap(), with area->pages being allocated in the kmalloc
> > >area.
> >
> > I think the above should not be a part of the commit message.
>
> Ah, yes.
>
> @maintainers: Feel free to remove that from the commit message. Or should I
> resend?

Please resend, never make a maintainer hand-edit a patch changelog :)

thanks,

greg k-h