linux-kernel - Re: [PATCH] eventfs: Test for ei->is

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Message-ID: <CA+G9fYuJF42KP-j5LNa2FMqDr8wxHFMXm2pNe=SRNnXvqKrMrQ@mail.gmail.com>
Date:   Sun, 29 Oct 2023 10:52:43 +0530
From:   Naresh Kamboju <naresh.kamboju@...aro.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux trace kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Beau Belgrave <beaub@...ux.microsoft.com>,
        Ajay Kaher <akaher@...are.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] eventfs: Test for ei->is_freed when accessing ei->dentry

On Sun, 29 Oct 2023 at 02:07, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
>
> The eventfs_inode (ei) is protected by SRCU, but the ei->dentry is not. It
> is protected by the eventfs_mutex. Anytime the eventfs_mutex is released,
> and access to the ei->dentry needs to be done, it should first check if
> ei->is_freed is set under the eventfs_mutex. If it is, then the ei->dentry
> is invalid and must not be used. The ei->dentry must only be accessed
> under the eventfs_mutex and after checking if ei->is_freed is set.
>
> When the ei is being freed, it will (under the eventfs_mutex) set is_freed
> and at the same time move the dentry to a free list to be cleared after
> the eventfs_mutex is released. This means that any access to the
> ei->dentry must check first if ei->is_freed is set, because if it is, then
> the dentry is on its way to be freed.
>
> Also add comments to describe this better.
>
> Link: https://lore.kernel.org/all/CA+G9fYt6pY+tMZEOg=SoEywQOe19fGP3uR15SGowkdK+_X85Cg@mail.gmail.com/
> Link: https://lore.kernel.org/all/CA+G9fYuDP3hVQ3t7FfrBAjd_WFVSurMgCepTxunSJf=MTe=6aA@mail.gmail.com/
>
> Fixes: 5790b1fb3d672 ("eventfs: Remove eventfs_file and just use eventfs_inode")
> Reported-by: Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>

In the above line "Reported-by:" is twice.

> Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
> Reported-by: Beau Belgrave <beaub@...ux.microsoft.com>
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>

I am running tests on this patch and will get back to you shortly.

- Naresh