[lxc-devel] [lxd/master] shared: Fix growing of buf in GroupId

[stgraber on Github]

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From 0c138f1f5a6f676b400ac41d091795543770cf67 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber at ubuntu.com>
Date: Thu, 24 Aug 2017 15:40:58 -0400
Subject: [PATCH] shared: Fix growing of buf in GroupId
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Closes #3711

Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>
---
 shared/util_linux.go | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/shared/util_linux.go b/shared/util_linux.go
index 02f380822..33747f191 100644
--- a/shared/util_linux.go
+++ b/shared/util_linux.go
@@ -411,7 +411,6 @@ func GroupId(name string) (int, error) {
 	if buf == nil {
 		return -1, fmt.Errorf("allocation failed")
 	}
-	defer C.free(buf)
 
 	cname := C.CString(name)
 	defer C.free(unsafe.Pointer(cname))
@@ -422,7 +421,7 @@ again:
 		(*C.char)(buf),
 		bufSize,
 		&result)
-	if rv < 0 {
+	if rv != 0 {
 		// OOM killer will take care of us if we end up doing this too
 		// often.
 		if errno == syscall.ERANGE {
@@ -434,8 +433,11 @@ again:
 			buf = tmp
 			goto again
 		}
+
+		C.free(buf)
 		return -1, fmt.Errorf("failed group lookup: %s", syscall.Errno(rv))
 	}
+	C.free(buf)
 
 	if result == nil {
 		return -1, fmt.Errorf("unknown group %s", name)