linux-kernel - Re: [RFC PATCH v4 1/5] glibc: Perform rseq(2) registration at nptl init and thread creation

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Message-ID: <87a7m1ywni.fsf@oldenburg.str.redhat.com>
Date:   Thu, 22 Nov 2018 16:11:45 +0100
From:   Florian Weimer <fweimer@...hat.com>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Rich Felker <dalias@...c.org>, carlos <carlos@...hat.com>,
        Joseph Myers <joseph@...esourcery.com>,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        libc-alpha <libc-alpha@...rceware.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ben Maurer <bmaurer@...com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will.deacon@....com>,
        Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>
Subject: Re: [RFC PATCH v4 1/5] glibc: Perform rseq(2) registration at nptl init and thread creation

* Mathieu Desnoyers:

> Thoughts ?
>
>   /* Unregister rseq TLS from kernel. */
>   if (has_rseq && __rseq_unregister_current_thread ())
>     abort();
>
>   advise_stack_range (pd->stackblock, pd->stackblock_size, (uintptr_t) pd,
>                       pd->guardsize);
>
>   /* If the thread is detached free the TCB.  */
>   if (IS_DETACHED (pd))
>     /* Free the TCB.  */
>     __free_tcb (pd);

Considering that we proceed to free the TCB, I really hope that all
signals are blocked at this point.  (I have not checked this, though.)

Wouldn't this address your concern about access to the rseq area?

Thanks,
Florian