handle some edge cases when dup2()ing /dev/null

1 files changed, 7 insertions, 5 deletions

diff --git a/ssh-agent-filter.C b/ssh-agent-filter.C
index 252e017..b806a85 100644
--- a/ssh-agent-filter.C
+++ b/ssh-agent-filter.C
@@ -602,11 +602,13 @@ int main (int const argc, char const * const * const argv) {
 		// the following stuff is optional, so we don't do error checking
 		setsid();
 		static_cast<void>(chdir("/"));
-		int devnull = open("/dev/null", O_RDWR);
-		dup2(devnull, 0);
-		dup2(devnull, 1);
-		dup2(devnull, 2);
-		close(devnull);
+		if (int devnull = open("/dev/null", O_RDWR); devnull != -1) {
+			dup2(devnull, 0);
+			dup2(devnull, 1);
+			dup2(devnull, 2);
+			if (devnull > 2)
+				close(devnull);
+		}
 	} else {
 		cout << "copy this to another terminal:" << endl;
 		cout << "SSH_AUTH_SOCK='" << path.native() << "'; export SSH_AUTH_SOCK;" << endl;