Fix bugs when (?!) is used as a condition.

ChangeLog

@@ -14,8 +14,16 @@ error. This bug was discovered by the LLVM fuzzer.
 
 4. Implemented pcre2_callout_enumerate().
 
-5. Fix JIT compilation of conditional blocks whose assertion
+5. Fix JIT compilation of conditional blocks whose assertion is converted to
-   is converted to (*FAIL). E.g: /(?(?!))/.
+(*FAIL). E.g: /(?(?!))/.
+
+6. The pattern /(?(?!)^)/ caused references to random memory. This bug was
+discovered by the LLVM fuzzer.
+
+7. The assertion (?!) is optimized to (*FAIL). This was not handled correctly
+when this assertion was used as a condition, for example (?(?!)a|b). In
+pcre2_match() it worked by luck; in pcre2_dfa_match() it gave an incorrect
+error about an unsupported item.
 
 
 Version 10.10 06-March-2015
@@ -120,12 +128,13 @@ repeated outer group that has a zero minimum quantifier, caused incorrect code
 to be compiled, leading to the error "internal error: previously-checked
 referenced subpattern not found" when an incorrect memory address was read.
 This bug was reported as "heap overflow", discovered by Kai Lu of Fortinet's
-FortiGuard Labs.
+FortiGuard Labs. (Added 24-March-2015: CVE-2015-2325 was given to this.)
 
 23. A pattern such as "((?+1)(\1))/" containing a forward reference subroutine
 call within a group that also contained a recursive back reference caused
 incorrect code to be compiled. This bug was reported as "heap overflow",
-discovered by Kai Lu of Fortinet's FortiGuard Labs.
+discovered by Kai Lu of Fortinet's FortiGuard Labs. (Added 24-March-2015:
+CVE-2015-2326 was given to this.)
 
 24. Computing the size of the JIT read-only data in advance has been a source
 of various issues, and new ones are still appear unfortunately. To fix

HACKING

@@ -210,7 +210,8 @@ These items are all just one unit long
   OP_THEN                )
 
 OP_ASSERT_ACCEPT is used when (*ACCEPT) is encountered within an assertion.
-This ends the assertion, not the entire pattern match.
+This ends the assertion, not the entire pattern match. The assertion (?!) is 
+always optimized to OP_FAIL.
 
 
 Backtracking control verbs with optional data
@@ -528,6 +529,10 @@ immediately before the assertion. It is also possible to insert a manual
 callout at this point. Only assertion conditions may have callouts preceding
 the condition.
 
+A condition that is the negative assertion (?!) is optimized to OP_FAIL in all 
+parts of the pattern, so this is another opcode that may appear as a condition. 
+It is treated the same as OP_FALSE.
+
 
 Recursion
 ---------

src/pcre2_compile.c

@@ -7284,7 +7284,7 @@ inside atomic brackets or in a pattern that contains *PRUNE or *SKIP does not
 count, because once again the assumption no longer holds.
 
 Arguments:
-  code           points to start of the compiled pattern
+  code           points to start of the compiled pattern or a group
   bracket_map    a bitmap of which brackets we are inside while testing; this
                    handles up to substring 31; after that we just have to take
                    the less precise approach
@@ -7321,6 +7321,7 @@ do {
        case OP_DNCREF:
        case OP_RREF:
        case OP_DNRREF:
+       case OP_FAIL:
        case OP_FALSE:
        case OP_TRUE:
        return FALSE;

src/pcre2_dfa_match.c

@@ -2660,14 +2660,15 @@ for (;;)
             condcode == OP_DNRREF)
           return PCRE2_ERROR_DFA_UCOND;
 
-        /* The DEFINE condition is always false */
+        /* The DEFINE condition is always false, and the assertion (?!) is
+        converted to OP_FAIL. */
         
-        if (condcode == OP_FALSE)
+        if (condcode == OP_FALSE || condcode == OP_FAIL)
           { ADD_ACTIVE(state_offset + codelink + LINK_SIZE + 1, 0); }
 
         /* There is also an always-true condition */
 
-        if (condcode == OP_TRUE)
+        else if (condcode == OP_TRUE)
           { ADD_ACTIVE(state_offset + LINK_SIZE + 2 + IMM2_SIZE, 0); }
 
         /* The only supported version of OP_RREF is for the value RREF_ANY,

src/pcre2_match.c

@@ -1408,6 +1408,7 @@ for (;;)
       break;
 
       case OP_FALSE:
+      case OP_FAIL:   /* The assertion (?!) becomes OP_FAIL */ 
       break;
 
       case OP_TRUE:

testdata/testinput2

@@ -4229,4 +4229,11 @@ a random value. /Ix
 / 61 28 3f 43 27 78 00 7a 27 29 62/hex,callout_info
     abcdefgh
 
+/(?(?!)^)/
+
+/(?(?!)a|b)/
+    bbb
+    ** Failers 
+    aaa 
+
 # End of testinput2 

testdata/testinput6

@@ -4846,4 +4846,8 @@
 / 61 28 3f 43 27 78 00 7a 27 29 62/hex
     abcdefgh
 
+/(?(?!)a|b)/
+    bbb
+    aaa 
+
 # End of testinput6

testdata/testoutput2

@@ -14188,4 +14188,14 @@ Callout (5): 'x\x00z'
     ^^           b
  0: ab
 
+/(?(?!)^)/
+
+/(?(?!)a|b)/
+    bbb
+ 0: b
+    ** Failers 
+No match
+    aaa 
+No match
+
 # End of testinput2 

testdata/testoutput6

@@ -7919,4 +7919,10 @@ Callout (5): 'x\x00z'
     ^^           b
  0: ab
 
+/(?(?!)a|b)/
+    bbb
+ 0: b
+    aaa 
+No match
+
 # End of testinput6