Re: [PATCH] af_unix: Don't set err in unix_stream_read_generic unless there was an error
From: Joseph Salisbury
Date: Thu Feb 11 2016 - 16:32:03 EST
On 02/05/2016 05:30 PM, Rainer Weikusat wrote:
> The present unix_stream_read_generic contains various code sequences of
> the form
>
> err = -EDISASTER;
> if (<test>)
> goto out;
>
> This has the unfortunate side effect of possibly causing the error code
> to bleed through to the final
>
> out:
> return copied ? : err;
>
> and then to be wrongly returned if no data was copied because the caller
> didn't supply a data buffer, as demonstrated by the program available at
>
> http://pad.lv/1540731
>
> Change it such that err is only set if an error condition was detected.
>
> Signed-off-by: Rainer Weikusat <rweikusat@xxxxxxxxxxxxxxxxxxxxxxx>
> ---
>
> With proper subject this time (at least I hope so).
>
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 49d5093..138787d 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -2277,13 +2277,15 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state)
> size_t size = state->size;
> unsigned int last_len;
>
> - err = -EINVAL;
> - if (sk->sk_state != TCP_ESTABLISHED)
> + if (sk->sk_state != TCP_ESTABLISHED) {
> + err = -EINVAL;
> goto out;
> + }
>
> - err = -EOPNOTSUPP;
> - if (flags & MSG_OOB)
> + if (flags & MSG_OOB) {
> + err = -EOPNOTSUPP;
> goto out;
> + }
>
> target = sock_rcvlowat(sk, flags & MSG_WAITALL, size);
> timeo = sock_rcvtimeo(sk, noblock);
> @@ -2329,9 +2331,11 @@ again:
> goto unlock;
>
> unix_state_unlock(sk);
> - err = -EAGAIN;
> - if (!timeo)
> + if (!timeo) {
> + err = -EAGAIN;
> break;
> + }
> +
> mutex_unlock(&u->readlock);
>
> timeo = unix_stream_data_wait(sk, timeo, last,
I tested your patch, Rainer. I can confirm that it fixes the reported
bug[0].
Thanks for the quick response!
Joe
[0] http://pad.lv/1540731