linux-kernel - Re: m68k: main.c:(.init.text+0x730): undefined reference to `strlen'

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Date:	Wed, 14 May 2008 19:14:07 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Andreas Schwab <schwab@...e.de>
Cc:	Adrian Bunk <bunk@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Linux/m68k <linux-m68k@...r.kernel.org>,
	Linux Kernel Development <linux-kernel@...r.kernel.org>
Subject: Re: m68k: main.c:(.init.text+0x730): undefined reference to
	`strlen'

[Andreas Schwab - Wed, May 14, 2008 at 04:55:37PM +0200]
| Cyrill Gorcunov <gorcunov@...il.com> writes:
| 
| > I think it would help to see ..tmp_vmlinux1.cmd to ensure for inclusion
| > of lib/lib.a. strlen was there without my patch as Andreas already pointed,
| > I've just added strncat wich is coming from lib/string.o for this arch.
| 
| Actually the way strncat is used here is broken anyway, it does not
| prevent array overrun.  The third argument of strncat only limits the
| amount of characters copied, without taking into account the length of
| the string already in the buffer.  Consequently gcc has optimized the
| call to strncat into a simple call to strcat, since none of the copied
| strings are longer than sizeof(msgbuf).  This strcat call is then
| expanded to include a call to strlen.
| 
| So a better fix would probably be to make msgbuf big enough and use
| strcat instead.
| 
| Andreas.
| 
| 

Andreas, could you test/review the following patch
(what is worse - I *have* introduced buffer overflow with my
patch, so I think we should fix it asap)
---

Index: linux-2.6.git/init/main.c
===================================================================
--- linux-2.6.git.orig/init/main.c	2008-05-14 17:55:10.000000000 +0400
+++ linux-2.6.git/init/main.c	2008-05-14 19:11:18.000000000 +0400
@@ -702,7 +702,7 @@ static void __init do_initcalls(void)

 	for (call = __initcall_start; call < __initcall_end; call++) {
 		ktime_t t0, t1, delta;
-		char msgbuf[40];
+		char msgbuf[64];
 		int result;

 		if (initcall_debug) {
@@ -729,11 +729,11 @@ static void __init do_initcalls(void)
 			sprintf(msgbuf, "error code %d ", result);

 		if (preempt_count() != count) {
-			strncat(msgbuf, "preemption imbalance ", sizeof(msgbuf));
+			strcat(msgbuf, "preemption imbalance ");
 			preempt_count() = count;
 		}
 		if (irqs_disabled()) {
-			strncat(msgbuf, "disabled interrupts ", sizeof(msgbuf));
+			strcat(msgbuf, "disabled interrupts ");
 			local_irq_enable();
 		}
 		if (msgbuf[0]) {
--
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