Re: [PATCH] vfs: avoid hang caused by attempting to rmdir an invalid file system

[Bernd Schubert <bernd.schubert@fastmail.fm>]

On 05/28/2012 07:33 PM, Theodore Ts'o wrote:
> If we rmdir a directory which is a hard link to '.', we will deadlock
> trying to grab the directory's i_mutex.  Check for this condition and
> return EINVAL, which is what we return if the user attempts to rmdir
> "/foo/bar/."
>
> Signed-off-by: "Theodore Ts'o"<tytso@mit.edu>
> ---
>   fs/namei.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index 0062dd1..081f872 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2774,6 +2774,17 @@ static long do_rmdir(int dfd, const char __user *pathname)
>   		error = -ENOENT;
>   		goto exit3;
>   	}
> +	if (nd.path.dentry->d_inode == dentry->d_inode) {

Shouldn't this be tagged as unlikely()?

> +		/*
> +		 * Corrupt file system where there is a symlink to
> +		 * '.'; treat it as if we are trying to rmdir '.'
> +		 *
> +		 * XXX Should we call into the low-level file system
> +		 * to request that the file system be marked corrupt?
> +		 */
> +		error = -EINVAL;
> +		goto exit3;
> +	}
>   	error = mnt_want_write(nd.path.mnt);
>   	if (error)
>   		goto exit3;

Thanks,
Bernd