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On 01/28/2015 03:30 PM, Sasha Levin wrote:
> We used to read file_handle twice. Once to get the amount of extra bytes, and
> once to fetch the entire structure.
>
> This may be problematic since we do size verifications only after the first
> read, so if the number of extra bytes changes in userspace between the first
> and second calls, we'll have an incoherent view of file_handle.
>
> Instead, read the constant size once, and copy that over to the final
> structure without having to re-read it again.
>
> Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
> ---
> Change in v2:
> - Use the f_handle pointer rather than size of struct
>
> fs/fhandle.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fhandle.c b/fs/fhandle.c
> index 999ff5c..d59712d 100644
> --- a/fs/fhandle.c
> +++ b/fs/fhandle.c
> @@ -195,8 +195,9 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
> goto out_err;
> }
> /* copy the full handle */
> - if (copy_from_user(handle, ufh,
> - sizeof(struct file_handle) +
> + *handle = f_handle;
> + if (copy_from_user(&handle->f_handle,
> + &ufh->f_handle,
> f_handle.handle_bytes)) {
> retval = -EFAULT;
> goto out_handle;
>
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