Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM?

From	Russell King - ARM Linux <linux@armlinux.org.uk>
Newsgroups	linux.kernel
Subject	Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM?
Date	2016-05-31 16:20 +0200
Message-ID	<rESGt-3N8-5@gated-at.bofh.it> (permalink)
References	<rEzNv-7IN-9@gated-at.bofh.it> <rED4K-1qz-41@gated-at.bofh.it> <rEEat-286-3@gated-at.bofh.it> <rESn7-3rp-3@gated-at.bofh.it>
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On Tue, May 31, 2016 at 02:52:52PM +0100, Will Deacon wrote:
> The only thing I'm uncertain of is whether or not PTRACE_SEIZE/PTRACE_LISTEN
> allow switching to the child (but even then, how is the parent doing
> to issue such a request?).

I can't see how that would be possible - the parent needs to finish
the vfp_set() call before it can issue any others - and there can
only be one tracer.  IOW, if we're in vfp_set(), the thread must
have attached to the child, at which point PTRACE_SEIZE will be
rejected.

PTRACE_LISTEN also requires the child to be in STOP state as well, and
again, can only be issued from the current tracer.

-- 
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Thread

Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM? Simon Marchi <simon.marchi@ericsson.com> - 2016-05-30 20:10 +0200
  Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM? Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-05-30 23:40 +0200
    Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM? Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-05-31 00:50 +0200
      Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM? Will Deacon <will.deacon@arm.com> - 2016-05-31 16:00 +0200
        Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM? Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-05-31 16:20 +0200
    Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM? Simon Marchi <simon.marchi@ericsson.com> - 2016-06-01 15:00 +0200
      Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM? Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-06-02 15:20 +0200
        Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM? Simon Marchi <simon.marchi@ericsson.com> - 2016-06-02 15:20 +0200

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