Patch: Fix libunwind segfault when -p is passed before -k

[Dmitry V. Levin]

Hi,

On Thu, Dec 08, 2016 at 10:00:59AM -1000, Sean Stangl wrote:
> There is a segfault if strace is called as `strace -p 2260 -k`.
> 
> The -k flag sets a global bool stack_trace_enabled. But -p already consults
> stack_trace_enabled during tcb initialization. So if -p is passed first,
> the libunwind components of the tcb are uninitialized.

Good catch, thanks!

> The attached patch fixes this issue by having -k ensure that the libunwind
> components are initialized.

I think the patch needs a guard against multiple -k options to avoid
multiple late_unwind_tcb_init() invocations.


-- 
ldv
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