From: Gustavo Sverzut Barbieri <barbieri@profusion.mobi>
Date: Tue, 3 Jan 2012 16:22:05 +0000 (-0200)
Subject: utils/read_str_safe(): fix wrong behavior and bugs.
X-Git-Tag: v3~20
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=671799415717ee6d10df48ce03d60c5d75cded9f;p=thirdparty%2Fkmod.git

utils/read_str_safe(): fix wrong behavior and bugs.

ouch, I did a mess in the original function, fix them:

 * on errors (read() < 0), continue reading after the done bytes, not
   at position 0.

 * read buflen - 1 bytes, so there is always room to store the
   trailing \0, as expected by user due behavior of snprintf(),
   fgets() and others.
---

diff --git a/libkmod/libkmod-util.c b/libkmod/libkmod-util.c
index a86eda39..75e2fea7 100644
--- a/libkmod/libkmod-util.c
+++ b/libkmod/libkmod-util.c
@@ -205,17 +205,18 @@ inline void *memdup(const void *p, size_t n)
 }
 
 ssize_t read_str_safe(int fd, char *buf, size_t buflen) {
-	size_t todo = buflen;
-	size_t done;
+	size_t todo = buflen - 1;
+	size_t done = 0;
 
 	do {
-		ssize_t r = read(fd, buf, todo);
+		ssize_t r = read(fd, buf + done, todo);
 
 		if (r == 0)
 			break;
-		else if (r > 0)
+		else if (r > 0) {
 			todo -= r;
-		else {
+			done += r;
+		} else {
 			if (errno == EAGAIN || errno == EWOULDBLOCK ||
 				errno == EINTR)
 				continue;
@@ -224,17 +225,7 @@ ssize_t read_str_safe(int fd, char *buf, size_t buflen) {
 		}
 	} while (todo > 0);
 
-	done = buflen - todo;
-
-	if (done == 0)
-		buf[0] = '\0';
-	else {
-		if (done < buflen)
-			buf[done] = '\0';
-		else if (buf[done - 1] != '\0')
-			return -ENOSPC;
-	}
-
+	buf[done] = '\0';
 	return done;
 }