lib: fd-util - Ensure fd is in valid range

diff --git a/src/lib/fd-util.c b/src/lib/fd-util.c
index 45dcfcf2d945747f8548f86c31461fee744a39d7..0456186595e14ec2c3498ba5285c6d7294abfe5d 100644 (file)
--- a/src/lib/fd-util.c
+++ b/src/lib/fd-util.c
@@ -99,6 +99,8 @@ void fd_set_nonblock(int fd, bool nonblock)
 {
        int flags;
 
+       i_assert(fd > -1);
+
        flags = fcntl(fd, F_GETFL, 0);
        if (flags < 0)
                i_fatal("fcntl(%d, F_GETFL) failed: %m", fd);