Fix decoding of sethostname syscall

The second argument of sethostname syscall is not an unsigned long but
unsigned int.  The kernel does not look at the string argument when
the length argument is too long.

* hostname.c [HAVE_LINUX_UTSNAME_H]: Include <linux/utsname.h>.
[!__NEW_UTS_LEN] (__NEW_UTS_LEN): Define.
(SYS_FUNC(sethostname)): Treat the second argument as unsigned int.
Print the first argument as a pointer when the second argument exceeds
__NEW_UTS_LEN.
* tests/sethostname.c [HAVE_LINUX_UTSNAME_H]: Include <linux/utsname.h>.
[!__NEW_UTS_LEN] (__NEW_UTS_LEN): Define.
(main): Use it.  Check that the second argument of sethostname
is handled as unsigned int.  Check that the first argument is printed
as a pointer when the second argument exceeds __NEW_UTS_LEN.

1 files changed, 17 insertions, 2 deletions

diff --git a/hostname.c b/hostname.c
index cc66f3ff2..394fdf605 100644
--- a/hostname.c
+++ b/hostname.c
@@ -1,9 +1,24 @@
 #include "defs.h"
 
+#ifdef HAVE_LINUX_UTSNAME_H
+# include <linux/utsname.h>
+#endif
+
+#ifndef __NEW_UTS_LEN
+# define __NEW_UTS_LEN 64
+#endif
+
 SYS_FUNC(sethostname)
 {
-	printstrn(tcp, tcp->u_arg[0], tcp->u_arg[1]);
-	tprintf(", %lu", tcp->u_arg[1]);
+	unsigned int len = tcp->u_arg[1];
+
+	if (len > __NEW_UTS_LEN) {
+		printaddr(tcp->u_arg[0]);
+	} else {
+		printstrn(tcp, tcp->u_arg[0], len);
+	}
+
+	tprintf(", %u", len);
 
 	return RVAL_DECODED;
 }