Commit 1b92ee3d authored Feb 08, 2016 by Rainer Weikusat Committed by David S. Miller Feb 16, 2016

af_unix: Don't set err in unix_stream_read_generic unless there was an error

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.

Fixes: 3822b5c2 ("af_unix: Revert 'lock_interruptible' in stream receive code")
Reported-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Signed-off-by: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent db92ea5d

net/unix/af_unix.c

+10 −6

Original line number	Diff line number	Diff line
		@@ -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;

		if (unlikely(sk->sk_state != TCP_ESTABLISHED)) {
		err = -EINVAL;
		if (sk->sk_state != TCP_ESTABLISHED)
		goto out;
		}

		if (unlikely(flags & MSG_OOB)) {
		err = -EOPNOTSUPP;
		if (flags & MSG_OOB)
		goto out;
		}

		target = sock_rcvlowat(sk, flags & MSG_WAITALL, size);
		timeo = sock_rcvtimeo(sk, noblock);
		@@ -2329,9 +2331,11 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state)
		goto unlock;

		unix_state_unlock(sk);
		if (!timeo) {
		err = -EAGAIN;
		if (!timeo)
		break;
		}

		mutex_unlock(&u->readlock);

		timeo = unix_stream_data_wait(sk, timeo, last,