[PATCH 2/9] check_sha1_signature: check return value from read_istream

[Jeff King <peff@peff.net>]

It's possible for read_istream to return an error, in which
case we just end up in an infinite loop (aside from EOF, we
do not even look at the result, but just feed it straight
into our running hash).

Signed-off-by: Jeff King <peff@peff.net>
---
I didn't actually trigger this code path in any of my tests, but I
audited all of the callers of read_istream after the last patch, and
noticed this one (the rest looked fine to me).

 sha1_file.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sha1_file.c b/sha1_file.c
index 16967d3..0b99f33 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1266,6 +1266,10 @@ int check_sha1_signature(const unsigned char *sha1, void *map,
 		char buf[1024 * 16];
 		ssize_t readlen = read_istream(st, buf, sizeof(buf));
 
+		if (readlen < 0) {
+			close_istream(st);
+			return -1;
+		}
 		if (!readlen)
 			break;
 		git_SHA1_Update(&c, buf, readlen);
-- 
1.8.2.13.g0f18d3c