From d0ff926dddff93fb5fd0333d21629a2ba9a33214 Mon Sep 17 00:00:00 2001
From: Vasil Dimov <vd@FreeBSD.org>
Date: Wed, 11 Dec 2019 11:51:32 +0100
Subject: [PATCH] ccan: fix read_all() to always set errno on failure

read(2) will return 0 to designate end-of-file and in this case it will
not set errno.

This is not considered as an error condition by read(2) itself, but all
callers of read_all() expect that exactly the requested number of bytes
will be read into the buffer, not less, so set errno to EBADMSG
"Bad message" in this case.

Related to https://github.com/ElementsProject/lightning/issues/3185
---
 ccan/ccan/read_write_all/read_write_all.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/ccan/ccan/read_write_all/read_write_all.c b/ccan/ccan/read_write_all/read_write_all.c
index 7f0b70b9d020..69289cd61396 100644
--- a/ccan/ccan/read_write_all/read_write_all.c
+++ b/ccan/ccan/read_write_all/read_write_all.c
@@ -26,12 +26,20 @@ bool read_all(int fd, void *data, size_t size)
 		ssize_t done;
 
 		done = read(fd, data, size);
-		if (done < 0 && errno == EINTR)
-			continue;
-		if (done <= 0)
+
+		switch (done) {
+		case -1:
+			if (errno == EINTR) {
+				continue;
+			}
 			return false;
-		data = (char *)data + done;
-		size -= done;
+		case 0:
+			errno = EBADMSG;
+			return false;
+		default:
+			data = (char *)data + done;
+			size -= done;
+		}
 	}
 
 	return true;