linux-kernel - Re: [PATCH] /proc/kcore: fix seeking

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Message-ID: <20110111005256.GC2570@nowhere>
Date:	Tue, 11 Jan 2011 01:52:59 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Dave Anderson <anderson@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH] /proc/kcore: fix seeking

(Adding stable and Andrew in Cc)

On Mon, Jan 10, 2011 at 09:42:29AM -0500, Dave Anderson wrote:
> From: Dave Anderson <anderson@...hat.com>
> 
> Commit 34aacb2920667d405a8df15968b7f71ba46c8f18
> ("procfs: Use generic_file_llseek in /proc/kcore")
> broke seeking on /proc/kcore.  This changes it back
> to use default_llseek in order to restore the original
> behavior.
> 
> The problem with generic_file_llseek is that it only
> allows seeks up to inode->i_sb->s_maxbytes, which is
> 2GB-1 on procfs, where the memory file offset values in
> the /proc/kcore PT_LOAD segments may exceed or start
> beyond that offset value.
> 
> A similar revert was made for /proc/vmcore.
> 
> Signed-off-by: Dave Anderson <anderson@...hat.com>
> Cc: Frederic Weisbecker <fweisbec@...il.com>

Acked-by: Frederic Weisbecker <fweisbec@...il.com>

In the longer term, I guess default_llseek should disappear
and replaced with generic_file_llseek(), tweaking the sb->s_maxbytes
with the appropriate values in each filesystems.

Thanks for this fix!


> --- linux-2.6.37/fs/proc/kcore.c.orig
> +++ linux-2.6.37/fs/proc/kcore.c
> @@ -558,7 +558,7 @@ static int open_kcore(struct inode *inod
>  static const struct file_operations proc_kcore_operations = {
>  	.read		= read_kcore,
>  	.open		= open_kcore,
> -	.llseek		= generic_file_llseek,
> +	.llseek		= default_llseek,
>  };
>  
>  #ifdef CONFIG_MEMORY_HOTPLUG

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