From 02afeaae9843733a39cd9b11053748b2d1dc5ae7 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Tue, 22 Dec 2015 14:52:38 -0800 Subject: [PATCH] x86/boot: Fix early command-line parsing when matching at end The x86 early command line parsing in cmdline_find_option_bool() is buggy. If it matches a specified 'option' all the way to the end of the command-line, it will consider it a match. For instance, cmdline = "foo"; cmdline_find_option_bool(cmdline, "fool"); will return 1. This is particularly annoying since we have actual FPU options like "noxsave" and "noxsaves" So, command-line "foo bar noxsave" will match *BOTH* a "noxsave" and "noxsaves". (This turns out not to be an actual problem because "noxsave" implies "noxsaves", but it's still confusing.) To fix this, we simplify the code and stop tracking 'len'. 'len' was trying to indicate either the NULL terminator *OR* the end of a non-NULL-terminated command line at 'COMMAND_LINE_SIZE'. But, each of the three states is *already* checking 'cmdline' for a NULL terminator. We _only_ need to check if we have overrun 'COMMAND_LINE_SIZE', and that we can do without keeping 'len' around. Also add some commends to clarify what is going on. 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/20151222225238.9AEB560C@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/lib/cmdline.c | 34 ++++++++++++++++++++++++---------- 1 file changed, 24 insertions(+), 10 deletions(-) diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c index 422db000d727..49548bed2301 100644 --- a/arch/x86/lib/cmdline.c +++ b/arch/x86/lib/cmdline.c @@ -21,12 +21,14 @@ static inline int myisspace(u8 c) * @option: option string to look for * * Returns the position of that @option (starts counting with 1) - * or 0 on not found. + * or 0 on not found. @option will only be found if it is found + * as an entire word in @cmdline. For instance, if @option="car" + * then a cmdline which contains "cart" will not match. */ int cmdline_find_option_bool(const char *cmdline, const char *option) { char c; - int len, pos = 0, wstart = 0; + int pos = 0, wstart = 0; const char *opptr = NULL; enum { st_wordstart = 0, /* Start of word/after whitespace */ @@ -37,11 +39,14 @@ int cmdline_find_option_bool(const char *cmdline, const char *option) if (!cmdline) return -1; /* No command line */ - len = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE); - if (!len) + if (!strlen(cmdline)) return 0; - while (len--) { + /* + * This 'pos' check ensures we do not overrun + * a non-NULL-terminated 'cmdline' + */ + while (pos < COMMAND_LINE_SIZE) { c = *(char *)cmdline++; pos++; @@ -58,17 +63,26 @@ int cmdline_find_option_bool(const char *cmdline, const char *option) /* fall through */ case st_wordcmp: - if (!*opptr) + if (!*opptr) { + /* + * We matched all the way to the end of the + * option we were looking for. If the + * command-line has a space _or_ ends, then + * we matched! + */ if (!c || myisspace(c)) return wstart; else state = st_wordskip; - else if (!c) + } else if (!c) { + /* + * Hit the NULL terminator on the end of + * cmdline. + */ return 0; - else if (c != *opptr++) + } else if (c != *opptr++) { state = st_wordskip; - else if (!len) /* last word and is matching */ - return wstart; + } break; case st_wordskip: