From 81765181c62bc02a5caa3dc25c32f30cd99ab659 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Fri, 11 Sep 2009 18:55:06 +0000
Subject: [PATCH] Backport: do not believe negative result from FIONREAD.

svn:r1429
---
 ChangeLog | 3 +++
 buffer.c  | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 2435c1f1..68c95f5f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,6 @@
+Changes in 1.4.13-stable:
+ o If the kernel tells us that there are a negative number of bytes to read from a socket, do not believe it.  Fixes bug 2841177; found by Alexander Pronchenkov.
+
 Changes in 1.4.12-stable:
  o Try to contain degree of failure when running on a win32 version so heavily firewalled that we can't fake a socketpair.
  o Fix an obscure timing-dependent, allocator-dependent crash in the evdns code.
diff --git a/buffer.c b/buffer.c
index 9cb0f0ce..6d1758d5 100644
--- a/buffer.c
+++ b/buffer.c
@@ -357,9 +357,9 @@ evbuffer_read(struct evbuffer *buf, int fd, int howmuch)
 #if defined(FIONREAD)
 #ifdef WIN32
 	long lng = n;
-	if (ioctlsocket(fd, FIONREAD, &lng) == -1 || (n=lng) == 0) {
+	if (ioctlsocket(fd, FIONREAD, &lng) == -1 || (n=lng) <= 0) {
 #else
-	if (ioctl(fd, FIONREAD, &n) == -1 || n == 0) {
+	if (ioctl(fd, FIONREAD, &n) == -1 || n <= 0) {
 #endif
 		n = EVBUFFER_MAX_READ;
 	} else if (n > EVBUFFER_MAX_READ && n > howmuch) {