Commit c75afa17 authored by Rainer Weikusat's avatar Rainer Weikusat Committed by Luis Henriques

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

commit 1b92ee3d upstream.

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: default avatarJoseph Salisbury <joseph.salisbury@canonical.com>
Signed-off-by: default avatarRainer Weikusat <rweikusat@mobileactivedefense.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
[ luis: backported to 3.16:
  - modify unix_stream_recvmsg() instead of unix_stream_read_generic()
  - adjusted context ]
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 8ae6af83
...@@ -2092,13 +2092,15 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, ...@@ -2092,13 +2092,15 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
long timeo; long timeo;
int skip; int skip;
err = -EINVAL; if (unlikely(sk->sk_state != TCP_ESTABLISHED)) {
if (sk->sk_state != TCP_ESTABLISHED) err = -EINVAL;
goto out; goto out;
}
err = -EOPNOTSUPP; if (unlikely(flags & MSG_OOB)) {
if (flags&MSG_OOB) err = -EOPNOTSUPP;
goto out; goto out;
}
target = sock_rcvlowat(sk, flags&MSG_WAITALL, size); target = sock_rcvlowat(sk, flags&MSG_WAITALL, size);
timeo = sock_rcvtimeo(sk, noblock); timeo = sock_rcvtimeo(sk, noblock);
...@@ -2146,9 +2148,11 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, ...@@ -2146,9 +2148,11 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
goto unlock; goto unlock;
unix_state_unlock(sk); unix_state_unlock(sk);
err = -EAGAIN; if (!timeo) {
if (!timeo) err = -EAGAIN;
break; break;
}
mutex_unlock(&u->readlock); mutex_unlock(&u->readlock);
timeo = unix_stream_data_wait(sk, timeo, last); timeo = unix_stream_data_wait(sk, timeo, last);
......
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