From: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Date: Mon, 8 Feb 2016 18:47:19 +0000 (+0000)
Subject: af_unix: Don't set err in unix_stream_read_generic unless there was an error
X-Git-Tag: firefly_0821_release~176^2~475^2~388
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=2f46f069ccfb28e6fdaa6798544fd30b72835b04;p=firefly-linux-kernel-4.4.55.git

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

[ Upstream commit 1b92ee3d03af6643df395300ba7748f19ecdb0c5 ]

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: 3822b5c2fc62 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 6de41c33a9db..265412c95d94 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2270,13 +2270,15 @@ 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 (unlikely(sk->sk_state != TCP_ESTABLISHED)) {
+		err = -EINVAL;
 		goto out;
+	}
 
-	err = -EOPNOTSUPP;
-	if (flags & MSG_OOB)
+	if (unlikely(flags & MSG_OOB)) {
+		err = -EOPNOTSUPP;
 		goto out;
+	}
 
 	target = sock_rcvlowat(sk, flags & MSG_WAITALL, size);
 	timeo = sock_rcvtimeo(sk, noblock);
@@ -2322,9 +2324,11 @@ 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,