linux-kernel - Re: [PATCH 6.6] membarrier: riscv: Add full memory barrier in switch_mm()

Open Source and information security mailing list archives

Message-ID: <364e0e33-68ad-4f0c-86f1-f6a95def9a30@ghiti.fr>
Date: Tue, 10 Sep 2024 13:31:04 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Greg KH <gregkh@...uxfoundation.org>, WangYuli <wangyuli@...ontech.com>
Cc: stable@...r.kernel.org, sashal@...nel.org, parri.andrea@...il.com,
 mathieu.desnoyers@...icios.com, palmer@...osinc.com,
 linux-kernel@...r.kernel.org, paul.walmsley@...ive.com, palmer@...belt.com,
 aou@...s.berkeley.edu, nathan@...nel.org, ndesaulniers@...gle.com,
 trix@...hat.com, linux-riscv@...ts.infradead.org, llvm@...ts.linux.dev,
 paulmck@...nel.org, mingo@...hat.com, peterz@...radead.org,
 juri.lelli@...hat.com, vincent.guittot@...aro.org, dietmar.eggemann@....com,
 rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
 bristot@...hat.com, vschneid@...hat.com, brauner@...nel.org, arnd@...db.de
Subject: Re: [PATCH 6.6] membarrier: riscv: Add full memory barrier in
 switch_mm()

Hi Greg,

On 10/09/2024 09:32, Greg KH wrote:
> On Mon, Sep 09, 2024 at 10:57:01AM +0800, WangYuli wrote:
>> From: Andrea Parri <parri.andrea@...il.com>
>>
>> [ Upstream commit d6cfd1770f20392d7009ae1fdb04733794514fa9 ]
>>
>> The membarrier system call requires a full memory barrier after storing
>> to rq->curr, before going back to user-space.  The barrier is only
>> needed when switching between processes: the barrier is implied by
>> mmdrop() when switching from kernel to userspace, and it's not needed
>> when switching from userspace to kernel.
>>
>> Rely on the feature/mechanism ARCH_HAS_MEMBARRIER_CALLBACKS and on the
>> primitive membarrier_arch_switch_mm(), already adopted by the PowerPC
>> architecture, to insert the required barrier.
>>
>> Fixes: fab957c11efe2f ("RISC-V: Atomic and Locking Code")
>> Signed-off-by: Andrea Parri <parri.andrea@...il.com>
>> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
>> Link: https://lore.kernel.org/r/20240131144936.29190-2-parri.andrea@gmail.com
>> Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
>> Signed-off-by: WangYuli <wangyuli@...ontech.com>
>> ---
>>   MAINTAINERS                         |  2 +-
>>   arch/riscv/Kconfig                  |  1 +
>>   arch/riscv/include/asm/membarrier.h | 31 +++++++++++++++++++++++++++++
>>   arch/riscv/mm/context.c             |  2 ++
>>   kernel/sched/core.c                 |  5 +++--
>>   5 files changed, 38 insertions(+), 3 deletions(-)
>>   create mode 100644 arch/riscv/include/asm/membarrier.h
> Now queued up, thanks.

The original patch was merged in 6.9 and the Fixes tag points to a 
commit introduced in v4.15. So IIUC, this patch should have been 
backported "automatically" to the releases < 6.9 right? As stated in the 
documentation (process/stable-kernel-rules.html):

"Note, such tagging is unnecessary if the stable team can derive the 
appropriate versions from Fixes: tags."

Or did we miss something?

Thanks,

Alex

>
> greg k-h
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

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