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List:       linux-api
Subject:    Re: [PATCH v8 1/2] seccomp: add a return code to trap to userspace
From:       Oleg Nesterov <oleg () redhat ! com>
Date:       2018-11-30 10:17:51
Message-ID: 20181130101751.GA23670 () redhat ! com
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On 11/29, Tycho Andersen wrote:
>
> /*
>  * These should never be seen by user programs.  To return one of ERESTART*
>  * codes, signal_pending() MUST be set.  Note that ptrace can observe these
>  * at syscall exit tracing, but they will never be left for the debugged user
>  * process to see.
>  */
> #define ERESTARTSYS     512
>
> So basically, if you respond with -ERESTARTSYS with no signal pending, you'll
> leak it to userspace.

Yes,

> It turns out this is already possible with
> SECCOMP_RET_TRAP (and probably ptrace alone,

Yes,

> The question is: do we care?

I think we do not care, debugger can do anything with the tracee.

Oleg.

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