linux-kernel - Re: [PATCH v4 43/45] namei: initialize parameters passed to step

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Message-ID: <CAHk-=wih_JHVPvp1qyW4KNK0ctTc6e+bDj4wdTgNkyND6tuFoQ@mail.gmail.com>
Date:   Mon, 4 Jul 2022 13:51:16 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Christoph Hellwig <hch@....de>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Kees Cook <keescook@...omium.org>,
        Marco Elver <elver@...gle.com>,
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        Matthew Wilcox <willy@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
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        Vlastimil Babka <vbabka@...e.cz>,
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        Segher Boessenkool <segher@...nel.crashing.org>,
        Vitaly Buka <vitalybuka@...gle.com>,
        linux-toolchains <linux-toolchains@...r.kernel.org>
Subject: Re: [PATCH v4 43/45] namei: initialize parameters passed to step_into()

On Mon, Jul 4, 2022 at 1:46 PM Al Viro <viro@...iv.linux.org.uk> wrote:
>
> Why is that a problem?  It could have been moved to another parent,
> but so it could after we'd crossed to the mounted and we wouldn't have
> noticed (or cared).

Yeah, see my other email.

I agree that it might be a "we don't actually care" situation, where
all we care about that the name was valid at one point (when we picked
up that sequence point). So maybe we don't care about closing it.

But even if so, I think it might warrant a comment, because I still
feel like we're basically "throwing away" our previous sequence point
information without ever checking it.

Maybe all we ever care about is basically "this sequence point
protects the dentry inode pointer for the next lookup", and when it
comes to mount points that ends up being immaterial.

             Linus