On Mon, Sep 20, 2010 at 08:04:09PM +0200, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@xxxxxxx>
>
> If open(O_TRUNC) is called and the actual open fails, then nd->path
> will be released by nameidata_to_filp(). If this races with an
> unmount then mnt_drop_write() can Oops.
>
> Fix by acquiring a ref to nd->path and releasing after
> mnt_drop_write().
>
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
> CC: stable@xxxxxxxxxx
> ---
> fs/namei.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> Index: linux-2.6/fs/namei.c
> ===================================================================
> --- linux-2.6.orig/fs/namei.c 2010-09-20 13:32:35.000000000 +0200
> +++ linux-2.6/fs/namei.c 2010-09-20 13:33:14.000000000 +0200
> @@ -1559,6 +1559,11 @@ static struct file *finish_open(struct n
> mnt_drop_write(nd->path.mnt);
> goto exit;
> }
> + if (will_truncate) {
> + /* nameidata_to_filp() puts nd->path! */
> + path_get(&nd->path);
> + }
> +
> filp = nameidata_to_filp(nd);
> if (!IS_ERR(filp)) {
> error = ima_file_check(filp, acc_mode);
> @@ -1581,8 +1586,10 @@ static struct file *finish_open(struct n
> * because the filp has had a write taken
> * on its behalf.
> */
> - if (will_truncate)
> + if (will_truncate) {
> mnt_drop_write(nd->path.mnt);
> + path_put(&nd->path);
> + }
> return filp;
>
> exit:
>
Nice catch!
Reviewed-by: Valerie Aurora <vaurora@xxxxxxxxxx>
-VAL
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