linux-kernel - [PATCH] ia32: strncpy does not null terminate string

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Message-ID: <4A60755F.4030604@gmail.com>
Date:	Fri, 17 Jul 2009 14:58:07 +0200
From:	Roel Kluin <roel.kluin@...il.com>
To:	mingo@...hat.com, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] ia32: strncpy does not null terminate string

With `sizeof(lastcomm) - 1` strncpy() will null terminate the string.

Signed-off-by: Roel Kluin <roel.kluin@...il.com>
---
To test this:

#include <stdio.h>
#include <string.h>

char a[10];
char b[10];

int main()
{
        const char* str = "0123456789012";
        strncpy(a, str, sizeof(a));
        strncpy(b, str, sizeof(b) - 1);
        printf("String a was %s, b was %s\n", a, b);

        return 0;
}

Output:
String a was 0123456789012345678, b was 012345678

diff --git a/arch/x86/ia32/sys_ia32.c b/arch/x86/ia32/sys_ia32.c
index 085a8c3..b114f57 100644
--- a/arch/x86/ia32/sys_ia32.c
+++ b/arch/x86/ia32/sys_ia32.c
@@ -687,7 +687,7 @@ long sys32_vm86_warning(void)
 		compat_printk(KERN_INFO
 			      "%s: vm86 mode not supported on 64 bit kernel\n",
 			      me->comm);
-		strncpy(lastcomm, me->comm, sizeof(lastcomm));
+		strncpy(lastcomm, me->comm, sizeof(lastcomm) - 1);
 	}
 	return -ENOSYS;
 }
--
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