linux-kernel - Re: stack frame unwindind KASAN errors

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Date:   Mon, 6 Mar 2017 10:40:08 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Daniel J Blueman <daniel@...ra.org>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: stack frame unwindind KASAN errors

On Mon, Mar 06, 2017 at 02:52:01PM +0800, Daniel J Blueman wrote:
> Thanks Josh!
> 
> With this patch, the KASAN warning still occurs, but at
> unwind_get_return_address+0x1d3/0x130 instead; the rest of the trace
> is identical.
> 
> (gdb) list *(unwind_get_return_address+0x1d3)
> 0xffffffff8112bca3 is in unwind_get_return_address
> (./include/linux/compiler.h:243).
> 238    })
> 239
> 240    static __always_inline
> 241    void __read_once_size(const volatile void *p, void *res, int size)
> 242    {
> 243        __READ_ONCE_SIZE;

Looking deeper, I have an idea about what's going on:

  https://quora.org/dmesg.txt

Each of the warnings seems to show an interrupt happening during an EFI
call.  I'm guessing EFI modified the frame pointer, at least
temporarily, which confused the unwinder :-(

Would it be possible for you to test again with 4.10?  It has some
additional unwinder output which should hopefully confirm my suspicions.

-- 
Josh