From 9bef27dec1a81b7ba46bc3126edd5ac1b225f6dc Mon Sep 17 00:00:00 2001
From: Jeremy Allison <jra@samba.org>
Date: Wed, 28 May 2014 10:40:27 -0700
Subject: [PATCH] s3: nmbd: Fix bug 10633 - nmbd denial of service

The Linux kernel has a bug in that it can give spurious
wakeups on a non-blocking UDP socket for a non-deliverable packet.

When nmbd was changed to use non-blocking sockets it
became vulnerable to a spurious wakeup from poll/epoll.

Fix sys_recvfile() to return on EWOULDBLOCK/EAGAIN.

CVE-2014-0244

Signed-off-by: Jeremy Allison <jra@samba.org>
---
 source3/lib/system.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/source3/lib/system.c b/source3/lib/system.c
index af72b2a..698de12 100644
--- a/source3/lib/system.c
+++ b/source3/lib/system.c
@@ -169,6 +169,7 @@ ssize_t sys_send(int s, const void *msg, size_t len, int flags)
 
 /*******************************************************************
 A recvfrom wrapper that will deal with EINTR.
+NB. As used with non-blocking sockets, return on EAGAIN/EWOULDBLOCK
 ********************************************************************/
 
 ssize_t sys_recvfrom(int s, void *buf, size_t len, int flags, struct sockaddr *from, socklen_t *fromlen)
@@ -177,11 +178,7 @@ ssize_t sys_recvfrom(int s, void *buf, size_t len, int flags, struct sockaddr *f
 
 	do {
 		ret = recvfrom(s, buf, len, flags, from, fromlen);
-#if defined(EWOULDBLOCK)
-	} while (ret == -1 && (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK));
-#else
-	} while (ret == -1 && (errno == EINTR || errno == EAGAIN));
-#endif
+	} while (ret == -1 && (errno == EINTR));
 	return ret;
 }
 
-- 
1.9.1.423.g4596e3a