From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 22 Sep 2017 19:05:03 +0000 (+0200)
Subject: fileio: initialize errno to zero before we do fread()
X-Git-Tag: v235.1~84
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=e0e02387f7dfc8ab4f415212264666476fc4a21f;p=elogind.git

fileio: initialize errno to zero before we do fread()

if there was something in the read buffer already errno might not be set
on error, let's detect that case.
---

diff --git a/src/basic/fileio.c b/src/basic/fileio.c
index 5dc303bb4..333effa5f 100644
--- a/src/basic/fileio.c
+++ b/src/basic/fileio.c
@@ -287,12 +287,13 @@ int read_full_stream(FILE *f, char **contents, size_t *size) {
                         return -ENOMEM;
 
                 buf = t;
+                errno = 0;
                 k = fread(buf + l, 1, n - l, f);
                 if (k > 0)
                         l += k;
 
                 if (ferror(f))
-                        return -errno;
+                        return errno > 0 ? -errno : -EIO;
 
                 if (feof(f))
                         break;