linux-kernel - Re: BUG: rseq selftests and librseq vs. glibc fail

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <lhuqzx7ygus.fsf@oldenburg.str.redhat.com>
Date: Tue, 19 Aug 2025 08:18:19 +0200
From: Florian Weimer <fweimer@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,  Jens Axboe <axboe@...nel.dk>,
  LKML <linux-kernel@...r.kernel.org>,  Michael Jeanson
 <mjeanson@...icios.com>,  Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>,  Peter Zijlstra <peterz@...radead.org>,
  "Paul E. McKenney" <paulmck@...nel.org>,  Boqun Feng
 <boqun.feng@...il.com>,  Wei Liu <wei.liu@...nel.org>,  Samuel Thibault
 <sthibault@...ian.org>
Subject: Re: BUG: rseq selftests and librseq vs. glibc fail

* Sean Christopherson:

>> If I make that:
>> 
>> +       if (!*libc_rseq_offset_p || !*libc_rseq_size_p) {
>> 
>> then it makes sense and actually works. The pointer can hardly be NULL,
>> even when statically linked, no?
>
> IIUC, it is indeed the pointers that are set to NULL/0, because for unresolved
> symbols, the symbol itself, not its value, is set to '0'.  Which makes sense,
> because if there is no symbol, then it can't have a value.

Right, that's how weak symbol references work.

Thanks,
Florian