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References: <20220519214021.3572840-1-kaleshsingh@google.com> <202205191848.DEE05F6@keescook>
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From:   Kalesh Singh <kaleshsingh@google.com>
Date:   Thu, 19 May 2022 21:01:39 -0700
Message-ID: <CAC_TJve0iyPU0uKoKOi_qcwgxPkgNKgirBcMJ=oYBqhRC3a_+Q@mail.gmail.com>
Subject: Re: [RFC PATCH] procfs: Add file path and size to /proc/<pid>/fdinfo
To:     Kees Cook <keescook@chromium.org>
Cc:     Ioannis Ilkos <ilkos@google.com>,
        "T.J. Mercier" <tjmercier@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        "Cc: Android Kernel" <kernel-team@android.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Anton Mitterer <mail@christoph.anton.mitterer.name>,
        Mike Rapoport <rppt@kernel.org>,
        Colin Cross <ccross@google.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
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On Thu, May 19, 2022 at 6:50 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, May 19, 2022 at 02:40:15PM -0700, Kalesh Singh wrote:
> > [...]
> > +     seq_file_path(m, file, "\n");
> > +     seq_putc(m, '\n');
> >
> >       /* show_fd_locks() never deferences files so a stale value is safe */
> >       show_fd_locks(m, file, files);
>
> This comment implies "file" might be stale? Does that mean anything for
> the above seq_file_path()?

Hi Kees.

Thanks for taking a look. The comment above says the "files" pointer
can be stale. It doesn't affect our use of "file" here. seq_show()
takes the reference with get_file() so "file" wouldn't be destroyed
from under us.

Thanks,
Kalesh
>
> --
> Kees Cook