[PATCH] tunctl: fix segfault on ioctl failure

[Dominique Martinet]

From: Dominique Martinet <dominique.martinet at atmark-techno.com>

libbb now takes "" instead of NULL as format string for nomsg functions,
but this caller had not been updated making busybox segfault on tunctl
commands when ioctl fails.
This can be reproduced by running `tunctl -t tun0` in gdb and blocking
with the tun open after being created, and running `tunctl -d tun0` in
another shell: the later will fail with EBUSY after fixing:
> tunctl: Device or resource busy

function                                             old     new   delta
tunctl_main                                          393     409     +16

Fixes: 4bd70463c7e7 ("libbb: pass "" rather than NULL as format string in _nomsg functions")
Signed-off-by: Dominique Martinet <dominique.martinet at atmark-techno.com>
---
Note this delta negates the benefit of the patch it fixes in term of
size, so it might actually be better to just revert that one instead...

 networking/tunctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/networking/tunctl.c b/networking/tunctl.c
index c17302eac1fb..cdb7eb659f35 100644
--- a/networking/tunctl.c
+++ b/networking/tunctl.c
@@ -54,7 +54,7 @@
 #define TUNSETGROUP _IOW('T', 206, int)
 #endif
 
-#define IOCTL(a, b, c) ioctl_or_perror_and_die(a, b, c, NULL)
+#define IOCTL(a, b, c) ioctl_or_perror_and_die(a, b, c, "")
 
 #if 1
 
-- 
2.39.5