On Fri, 2010-07-30 at 15:09 +0400, Kulikov Vasiliy wrote:
> copy_to_user() returns nonzero value on error, this value may be any
> value between 0 and requested count, not only requested count.
>
> Signed-off-by: Kulikov Vasiliy <segooon@xxxxxxxxx>
> ---
> fs/nfs/idmap.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
> index 21a84d4..a9f2cd5 100644
> --- a/fs/nfs/idmap.c
> +++ b/fs/nfs/idmap.c
> @@ -362,7 +362,7 @@ idmap_pipe_upcall(struct file *filp, struct rpc_pipe_msg *msg,
> unsigned long left;
>
> left = copy_to_user(dst, data, mlen);
> - if (left == mlen) {
> + if (left)
> msg->errno = -EFAULT;
> return -EFAULT;
> }
...and we do handle the case where copy_to_user returns less than the
requested number of bytes: it is called a 'short read' and is quite
allowed in POSIX. The userland application can just call sys_read()
again...
Trond
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