linux-kernel - [PATCH 5/5] x86: simplify early command line parsing

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Message-Id: <20151217220101.F736D3E3@viggo.jf.intel.com>
Date:	Thu, 17 Dec 2015 14:01:01 -0800
From:	Dave Hansen <dave@...1.net>
To:	linux-kernel@...r.kernel.org
Cc:	Dave Hansen <dave@...1.net>, dave.hansen@...ux.intel.com,
	bp@...e.de, hpa@...or.com, fenghua.yu@...el.com,
	yu-cheng.yu@...el.com
Subject: [PATCH 5/5] x86: simplify early command line parsing


From: Dave Hansen <dave.hansen@...ux.intel.com>

__cmdline_find_option_bool() tries to account for both
NULL-terminated and non-NULL-terminated strings.  It keeps 'pos'
to look for the end of the buffer and also looks for '!c' in a
bunch of places to look for NULL termination.

But, it also calls strlen().  You can't call strlen on a
non-NULL-terminated string.

If !strlen(cmdline), then cmdline[0]=='\0'.  In that case, we
will go in to the while() loop, set c='\0', hit st_wordstart,
notice !c, and will immediately return 0.

So, remove the strlen().  It is unnecessary and unsafe.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: linux-kernel@...r.kernel.org
Cc: fenghua.yu@...el.com
Cc: yu-cheng.yu@...el.com
---

 b/arch/x86/lib/cmdline.c |    3 ---
 1 file changed, 3 deletions(-)

diff -puN arch/x86/lib/cmdline.c~x86-early-command-line-non-term arch/x86/lib/cmdline.c
--- a/arch/x86/lib/cmdline.c~x86-early-command-line-non-term	2015-12-17 13:54:54.211004070 -0800
+++ b/arch/x86/lib/cmdline.c	2015-12-17 13:54:54.214004206 -0800
@@ -41,9 +41,6 @@ static int __cmdline_find_option_bool(co
 	if (!cmdline)
 		return -1;      /* No command line */
 
-	if (!strlen(cmdline))
-		return 0;
-
 	/*
 	 * This 'pos' check ensures we do not overrun
 	 * a non-NULL-terminated 'cmdline'
_
--
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