linux-kernel - Re: [PATCH] mm: Fix access_remote_vm() regression on tagged addresses

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Date:   Wed, 9 Aug 2023 08:05:36 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Taras Madan <tarasmadan@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Christina Schimpe <christina.schimpe@...el.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH] mm: Fix access_remote_vm() regression on tagged addresses

On Wed, 9 Aug 2023 at 07:46, Kirill A. Shutemov
<kirill.shutemov@...ux.intel.com> wrote:
>
> mem_rw() of procfs uses access_remote_vm() to get data from the target
> process. It worked fine until recent changes in __access_remote_vm()
> that now checks if there's VMA at target address using raw address.
>
> Untag the address before looking up the VMA.

Interesting that it took this long to notice.

Not surprising considering that LAM isn't actually available, but I'd
have expected the arm people to notice more. Yes, I have (and test) my
arm64 laptop, but I obviously don't do user space debugging on it.
Apparently others don't either.

Or maybe TBI is used a lot less than I thought.

Anyway, obviously applied,

            Linus