Fix exponential behavior in glob() with respect to multiple '*'.

See https://research.swtch.com/glob
Adapted from https://perl5.git.perl.org/perl.git/commit/33252c318625f3c6c89b816ee88481940e3e6f95

diff --git a/lib/util/glob.c b/lib/util/glob.c
index ee59642d428e6bb3d467cc9a236f7671255475e1..ac19f86d71515b0b62cd18a70dd2a4e2153d72bc 100644 (file)
--- a/lib/util/glob.c
+++ b/lib/util/glob.c
@@ -135,9 +135,6 @@ typedef char Char;
 #define        GLOB_LIMIT_STAT         2048
 #define        GLOB_LIMIT_READDIR      16384
 
-/* Limit of recursion during matching attempts. */
-#define        GLOB_LIMIT_RECUR        64
-
 struct glob_lim {
        size_t  glim_malloc;
        size_t  glim_stat;
@@ -164,7 +161,7 @@ static const Char *
 static int      globexp1(const Char *, glob_t *, struct glob_lim *);
 static int      globexp2(const Char *, const Char *, glob_t *,
                    struct glob_lim *);
-static int      match(Char *, Char *, Char *, int);
+static int      match(Char *, Char *, Char *);
 #ifdef DEBUG
 static void     qprintf(const char *, Char *);
 #endif
@@ -699,7 +696,7 @@ glob3(Char *pathbuf, Char *pathbuf_last, Char *pathend, Char *pathend_last,
                        break;
                }
 
-               if (!match(pathend, pattern, restpattern, GLOB_LIMIT_RECUR)) {
+               if (!match(pathend, pattern, restpattern)) {
                        *pathend = EOS;
                        continue;
                }
@@ -790,17 +787,24 @@ globextend(const Char *path, glob_t *pglob, struct glob_lim *limitp,
 
 /*
  * pattern matching function for filenames.  Each occurrence of the *
- * pattern causes a recursion level.
+ * pattern causes an iteration.
+ *
+ * Note, this function differs from the original as per the discussion
+ * here: https://research.swtch.com/glob
+ *
+ * Basically we removed the recursion and made it use the algorithm
+ * from Russ Cox to not go quadratic on cases like a file called
+ * ("a" x 100) . "x" matched against a pattern like "a*a*a*a*a*a*a*y".
  */
 static int
-match(Char *name, Char *pat, Char *patend, int recur)
+match(Char *name, Char *pat, Char *patend)
 {
        int ok, negate_range;
        Char c, k;
+       Char *nextp = NULL;
+       Char *nextn = NULL;
 
-       if (recur-- == 0)
-               return GLOB_NOSPACE;
-
+loop:
        while (pat < patend) {
                c = *pat++;
                switch (c & M_MASK) {
@@ -809,19 +813,19 @@ match(Char *name, Char *pat, Char *patend, int recur)
                                pat++;  /* eat consecutive '*' */
                        if (pat == patend)
                                return 1;
-                       do {
-                           if (match(name, pat, patend, recur))
-                                   return 1;
-                       } while (*name++ != EOS);
-                       return 0;
+                       if (*name == EOS)
+                               return 0;
+                       nextn = name + 1;
+                       nextp = pat - 1;
+                       break;
                case M_ONE:
                        if (*name++ == EOS)
-                               return 0;
+                               goto fail;
                        break;
                case M_SET:
                        ok = 0;
                        if ((k = *name++) == EOS)
-                               return 0;
+                               goto fail;
                        if ((negate_range = ((*pat & M_MASK) == M_NOT)) != EOS)
                                ++pat;
                        while (((c = *pat++) & M_MASK) != M_END) {
@@ -840,15 +844,23 @@ match(Char *name, Char *pat, Char *patend, int recur)
                                        ok = 1;
                        }
                        if (ok == negate_range)
-                               return 0;
+                               goto fail;
                        break;
                default:
                        if (*name++ != c)
-                               return 0;
+                               goto fail;
                        break;
                }
        }
-       return *name == EOS;
+       if (*name == EOS)
+               return 1;
+fail:
+       if (nextn) {
+               pat = nextp;
+               name = nextn;
+               goto loop;
+       }
+       return 0;
 }
 
 /* Free allocated data belonging to a glob_t structure. */