linux-kernel - Re: Memory keys and io

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Message-ID: <1cbf2f0b-7833-8a6c-e371-f648ebcb94a6@intel.com>
Date:   Thu, 11 Feb 2021 23:30:41 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Jens Axboe <axboe@...nel.dk>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: Memory keys and io_uring.

On 2/11/21 10:59 PM, Aneesh Kumar K.V wrote:
> A read syscall do fail with EFAULT. But we allow read via io_uring
> syscalls. Is that ok? 

In short, yes.

As much as I'd like to apply pkey permissions to all accesses, when we
don't have the CPU registers around, we don't have a choice: we have to
let the access through.

The same basic thing is done for accesses via the IOMMU and for things
like ptrace() where the ptracer's registers don't have anything to do
with the ptracee's address space.

We could *probably* be a bit pickier at io_uring_submit() time.  But,
I'm not sure it's worth it.