From: Jens Axboe <axboe@kernel.dk>
To: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: treat PF_IO_WORKER like PF_KTHREAD for mitigations
Date: Thu, 26 Jan 2023 07:07:45 -0700 [thread overview]
Message-ID: <012e38c7-8cb9-a65c-a553-e8a2fafe6f3b@kernel.dk> (raw)
In-Reply-To: <20230126140017.GD29148@willie-the-truck>
On 1/26/23 7:00 AM, Will Deacon wrote:
> On Wed, Jan 25, 2023 at 09:43:34AM -0700, Jens Axboe wrote:
>> Like PF_KTHREAD, PF_IO_WORKER never exit to userspace. They exist
>> entirely within the kernel, and hence don't need any task mitigations
>> applied.
>>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>
>> ---
>>
>> diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c
>> index fca9cc6f5581..25a21c3d446c 100644
>> --- a/arch/arm64/kernel/proton-pack.c
>> +++ b/arch/arm64/kernel/proton-pack.c
>> @@ -654,7 +654,7 @@ static void __update_pstate_ssbs(struct pt_regs *regs, bool state)
>> void spectre_v4_enable_task_mitigation(struct task_struct *tsk)
>> {
>> struct pt_regs *regs = task_pt_regs(tsk);
>> - bool ssbs = false, kthread = tsk->flags & PF_KTHREAD;
>> + bool ssbs = false, kthread = tsk->flags & (PF_KTHREAD | PF_IO_WORKER);
>
> Hmm, the other two uses of PF_KTHREAD in arch/arm64 also look pretty
> suspect in light of this proposal. Should we also update
> ssbs_thread_switch() and access_ok()? If not, then a comment would be
> handy to say why PF_KTHREAD is sufficient there.
The uaccess one looks like, PF_IO_WORKER threads are just normal userspace
threads. The only difference is that they never exit to userspace, they
remain in the kernel. But everything else is just like a thread.
But yes, the ssbs_thread_switch() should have this check too. I'll send
out an updated patch.
--
Jens Axboe
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next prev parent reply other threads:[~2023-01-26 14:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-25 16:43 [PATCH] arm64: treat PF_IO_WORKER like PF_KTHREAD for mitigations Jens Axboe
2023-01-26 14:00 ` Will Deacon
2023-01-26 14:07 ` Jens Axboe [this message]
2023-01-26 15:04 ` Catalin Marinas
2023-03-28 14:14 ` Will Deacon
2023-03-28 16:47 ` Jens Axboe
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