From abcdc1c694fa4055323cbec1cde4c2cb6b68398c Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Tue, 22 Dec 2015 14:52:39 -0800 Subject: [PATCH] x86/boot: Fix early command-line parsing when partial word matches cmdline_find_option_bool() keeps track of position in two strings: 1. the command-line 2. the option we are searchign for in the command-line We plow through each character in the command-line one at a time, always moving forward. We move forward in the option ('opptr') when we match characters in 'cmdline'. We reset the 'opptr' only when we go in to the 'st_wordstart' state. But, if we fail to match an option because we see a space (state=st_wordcmp, *opptr='\0',c=' '), we set state='st_wordskip' and 'break', moving to the next character. But, that move to the next character is the one *after* the ' '. This means that we will miss a 'st_wordstart' state. For instance, if we have cmdline = "foo fool"; and are searching for "fool", we have: "fool" opptr = ----^ "foo fool" c = --------^ We see that 'l' != ' ', set state=st_wordskip, break, and then move 'c', so: "foo fool" c = ---------^ and are still in state=st_wordskip. We will stay in wordskip until we have skipped "fool", thus missing the option we were looking for. This *only* happens when you have a partially- matching word followed by a matching one. To fix this, we always fall *into* the 'st_wordskip' state when we set it. Signed-off-by: Dave Hansen Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: fenghua.yu@intel.com Cc: yu-cheng.yu@intel.com Link: http://lkml.kernel.org/r/20151222225239.8E1DCA58@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/lib/cmdline.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c index 49548bed2301..ff8d1beead6c 100644 --- a/arch/x86/lib/cmdline.c +++ b/arch/x86/lib/cmdline.c @@ -72,18 +72,26 @@ int cmdline_find_option_bool(const char *cmdline, const char *option) */ if (!c || myisspace(c)) return wstart; - else - state = st_wordskip; + /* + * We hit the end of the option, but _not_ + * the end of a word on the cmdline. Not + * a match. + */ } else if (!c) { /* * Hit the NULL terminator on the end of * cmdline. */ return 0; - } else if (c != *opptr++) { - state = st_wordskip; + } else if (c == *opptr++) { + /* + * We are currently matching, so continue + * to the next character on the cmdline. + */ + break; } - break; + state = st_wordskip; + /* fall through */ case st_wordskip: if (!c) -- 2.20.1