Re: x86: warning in unwind_get_return_address

On Tue, Dec 20, 2016 at 03:43:27PM +0100, Andrey Konovalov wrote:

Hi,

I've got the following warning while running the syzkaller fuzzer:

WARNING: unrecognized kernel stack return address ffffffffa0000001 at
ffff88006377fa18 in a.out:4467

By adding a BUG() to unwind_get_return_address() I was able to capture
the stack trace (see below). Looks like unwind_get_return_address()
gets called when KASAN tries to unwind the stack to save the stack
trace.

A reproducer is attached. CONFIG_KASAN=y is most likely needed for it to work.

Hi Andrey,

I've tried with your reproducer but it didn't recreate.  Can you try
again with the following patch from the tip tree, instead of your BUG()
patch?

  http://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/patch/?id=8b5e99f02264130782a10ba5c0c759797fb064ee

That will dump the stack data, which should give more clues about what
went wrong.

-- 
Josh

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