linux-kernel - Re: [PATCH 1/2] sysfs: fix race between readdir and lseek

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Date:	Thu, 21 Mar 2013 10:41:04 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	Ming Lei <ming.lei@...onical.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH 1/2] sysfs: fix race between readdir and lseek

On 2013/3/20 23:25, Ming Lei wrote:
> While readdir() is running, lseek() may set filp->f_pos as zero,
> then may leave filp->private_data pointing to one sysfs_dirent
> object without holding its reference counter, so the sysfs_dirent
> object may be used after free in next readdir().
> 
> This patch holds inode->i_mutex to avoid the problem since
> the lock is always held in readdir path.
> 

In fact the same race exists between readdir() and read()/write()...

> Reported-by: Dave Jones <davej@...hat.com>
> Tested-by: Sasha Levin <levinsasha928@...il.com>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Ming Lei <ming.lei@...onical.com>
> ---
>  fs/sysfs/dir.c |   13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)

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