Re: [PATCH] tty: add lockdep annotations

[Eric Dumazet]

On Fri, 2012-06-01 at 21:56 +0100, Alan Cox wrote:
> > Yes, tty->driver deref is ok (tty points to valid memory), but crash is
> > on tty->driver->ops (driver points to freed/illegal memory)
> > 
> > using slub_debug=FZPU, I can indeed see RDI=6b6b6b6b6b6b6b6b
> 
> driver and driver->ops is basically const and it's not what you'd expect
> from a tty refcount bug. The driver side puts shouldn't have changed but
> I'll take a look over that patch and the error paths closely again just
> in case.

right

The code looks like :
...
	call mcount
	mov  %rdi,%rbx
	mov  0x10(%rdi),%rdi   tty->driver
<>	mov  0xf8(%rdi),%rax   CRASH

So tty was freed an tty->driver contains 6b6b6b6b6b6b6b6b



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