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From: Andrew Morton <>
To: Masatake YAMATO <>
Cc:,,, Kees Cook <>
Subject: Re: [PATCH RESEND] eventfd: prepare id to userspace via fdinfo
Date: Wed, 20 Mar 2019 12:05:25 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, 20 Mar 2019 18:29:29 +0900 Masatake YAMATO <> wrote:

> Finding endpoints of an IPC channel is one of essential task to
> understand how a user program works. Procfs and netlink socket provide
> enough hints to find endpoints for IPC channels like pipes, unix
> sockets, and pseudo terminals. However, there is no simple way to find
> endpoints for an eventfd file from userland. An inode number doesn't
> hint. Unlike pipe, all eventfd files share the same inode object.
> To provide the way to find endpoints of an eventfd file, this patch
> adds "eventfd-id" field to /proc/PID/fdinfo of eventfd as identifier.
> Address for eventfd context is used as id.
> A tool like lsof can utilize the information to print endpoints.
> ...
> --- a/fs/eventfd.c
> +++ b/fs/eventfd.c
> @@ -297,6 +297,7 @@ static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
>  	seq_printf(m, "eventfd-count: %16llx\n",
>  		   (unsigned long long)ctx->count);
>  	spin_unlock_irq(&ctx->wqh.lock);
> +	seq_printf(m, "eventfd-id: %p\n", ctx);
>  }
>  #endif

Is it a good idea to use a bare kernel address for this?  How does this
interact with printk pointer randomization and hashing?

  reply	other threads:[~2019-03-20 19:05 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-20  9:29 [PATCH RESEND] eventfd: prepare id to userspace via fdinfo Masatake YAMATO
2019-03-20 19:05 ` Andrew Morton [this message]
2019-03-21  3:37   ` Masatake YAMATO
  -- strict thread matches above, loose matches on Subject: below --
2019-03-06  7:08 Masatake YAMATO
2019-02-05 11:46 Masatake YAMATO

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