From: Florian Weimer <fweimer@redhat.com>
To: Szabolcs Nagy via Libc-alpha <libc-alpha@sourceware.org>
Cc: Szabolcs Nagy <szabolcs.nagy@arm.com>
Subject: Re: [PATCH v2 08/14] elf: Fix DTV gap reuse logic [BZ #27135]
Date: Thu, 24 Jun 2021 14:27:56 +0200 [thread overview]
Message-ID: <87v963jvlf.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <878s2zlhjp.fsf@oldenburg.str.redhat.com> (Florian Weimer's message of "Thu, 24 Jun 2021 11:48:26 +0200")
* Florian Weimer:
> * Szabolcs Nagy via Libc-alpha:
>
>> For some reason only dlopen failure caused dtv gaps to be reused.
>>
>> It is possible that the intent was to never reuse modids for a
>> different module, but after dlopen failure all gaps are reused
>> not just the ones caused by the unfinished dlopened.
>>
>> So the code has to handle reused modids already which seems to
>> work, however the data races at thread creation and tls access
>> (see bug 19329 and bug 27111) may be more severe if slots are
>> reused so this is scheduled after those fixes. I think fixing
>> the races are not simpler if reuse is disallowed and reuse has
>> other benefits, so set GL(dl_tls_dtv_gaps) whenever entries are
>> removed from the middle of the slotinfo list. The value does
>> not have to be correct: incorrect true value causes the next
>> modid query to do a slotinfo walk, incorrect false will leave
>> gaps and new entries are added at the end.
>>
>> Fixes bug 27135.
>> ---
>> elf/dl-close.c | 6 +++++-
>> elf/dl-open.c | 10 ----------
>> elf/dl-tls.c | 5 +----
>> 3 files changed, 6 insertions(+), 15 deletions(-)
>
> Apparently this broke GNOME Shell:
>
> <https://bugzilla.redhat.com/show_bug.cgi?id=1974970>
>
> I'm trying to figure out why.
The bug is that if there is a gap, _dl_next_tls_modid does not update
the slotinfo list to mark the modid to be returned as reserved, so
multiple calls in a single dlopen operation keep returning the same
modid.
I'm not yet sure what the proper fix is for that.
Thanks,
Florian
next prev parent reply other threads:[~2021-06-24 12:28 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 8:17 [PATCH v2 00/14] Dynamic TLS related data race fixes Szabolcs Nagy
2021-04-13 8:18 ` [PATCH v2 01/14] elf: Fix a DTV setup issue [BZ #27136] Szabolcs Nagy
2021-04-13 8:36 ` Andreas Schwab
2021-04-13 9:35 ` Szabolcs Nagy
2021-04-13 10:22 ` Andreas Schwab
2021-04-13 10:34 ` Szabolcs Nagy
2021-04-13 10:51 ` Andreas Schwab
2021-04-13 8:18 ` [PATCH v2 02/14] elf: Add a DTV setup test " Szabolcs Nagy
2021-04-14 18:06 ` Adhemerval Zanella
2021-04-15 9:53 ` Szabolcs Nagy
2021-04-13 8:18 ` [PATCH v2 03/14] elf: Fix comments and logic in _dl_add_to_slotinfo Szabolcs Nagy
2021-04-14 18:12 ` Adhemerval Zanella
2021-04-13 8:18 ` [PATCH v2 04/14] elf: Refactor _dl_update_slotinfo to avoid use after free Szabolcs Nagy
2021-04-14 18:20 ` Adhemerval Zanella
2021-04-13 8:19 ` [PATCH v2 05/14] elf: Fix data races in pthread_create and TLS access [BZ #19329] Szabolcs Nagy
2021-04-15 17:44 ` Adhemerval Zanella
2021-04-13 8:19 ` [PATCH v2 06/14] elf: Use relaxed atomics for racy accesses " Szabolcs Nagy
2021-04-15 18:21 ` Adhemerval Zanella
2021-04-16 9:12 ` Szabolcs Nagy
2021-05-11 2:56 ` Carlos O'Donell
2021-05-11 9:31 ` Szabolcs Nagy
2021-05-11 16:19 ` Szabolcs Nagy
2021-05-12 20:33 ` Carlos O'Donell
2021-04-13 8:19 ` [PATCH v2 07/14] elf: Add test case for " Szabolcs Nagy
2021-04-15 19:21 ` Adhemerval Zanella
2021-04-13 8:20 ` [PATCH v2 08/14] elf: Fix DTV gap reuse logic [BZ #27135] Szabolcs Nagy
2021-04-15 19:45 ` Adhemerval Zanella
2021-06-24 9:48 ` Florian Weimer
2021-06-24 12:27 ` Florian Weimer [this message]
2021-06-24 12:57 ` Adhemerval Zanella
2021-06-24 14:20 ` Florian Weimer
2021-06-24 18:58 ` Szabolcs Nagy
2021-04-13 8:20 ` [PATCH v2 09/14] x86_64: Avoid lazy relocation of tlsdesc [BZ #27137] Szabolcs Nagy
2021-04-13 14:02 ` H.J. Lu
2021-04-13 8:20 ` [PATCH v2 10/14] i386: " Szabolcs Nagy
2021-04-13 14:02 ` H.J. Lu
2021-04-13 8:21 ` [PATCH v2 11/14] x86_64: Remove lazy tlsdesc relocation related code Szabolcs Nagy
2021-04-13 14:03 ` H.J. Lu
2021-04-13 8:21 ` [PATCH v2 12/14] i386: " Szabolcs Nagy
2021-04-13 14:04 ` H.J. Lu
2021-04-13 8:21 ` [PATCH v2 13/14] elf: " Szabolcs Nagy
2021-04-15 19:52 ` Adhemerval Zanella
2021-04-13 8:21 ` [PATCH v2 14/14] RFC elf: Fix slow tls access after dlopen [BZ #19924] Szabolcs Nagy
2022-09-16 9:54 ` Carlos O'Donell
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