x86/boot: Fix early command-line parsing when matching at end

[cascardo/linux.git] / arch / x86 / lib / cmdline.c

diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index 422db00..49548be 100644 (file)
--- 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: