[tip:x86/boot] x86/boot: Simplify early command line parsing

[tip-bot for Dave Hansen]

Commit-ID:  4de07ea481361b08fe13735004dafae862482d38
Gitweb:     http://git.kernel.org/tip/4de07ea481361b08fe13735004dafae862482d38
Author:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
AuthorDate: Tue, 22 Dec 2015 14:52:41 -0800
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 3 Feb 2016 12:03:17 +0100

x86/boot: Simplify early command line parsing

__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@xxxxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: fenghua.yu@xxxxxxxxx
Cc: yu-cheng.yu@xxxxxxxxx
Link: http://lkml.kernel.org/r/20151222225241.15365E43@xxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/lib/cmdline.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index ff8d1be..945a639 100644
--- a/arch/x86/lib/cmdline.c
+++ b/arch/x86/lib/cmdline.c
@@ -39,9 +39,6 @@ int cmdline_find_option_bool(const char *cmdline, const char *option)
 	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'