bpo-23689: re module, fix memory leak when a match is terminated by a signal or memory allocation failure (GH-32283)

Author: Ma Lin

Lib/re/_compiler.py

@@ -67,14 +67,21 @@
 _ignorecase_fixes = {i: tuple(j for j in t if i != j)
                      for t in _equivalences for i in t}
 
+class _CompileData:
+    __slots__ = ('code', 'repeat_count')
+    def __init__(self):
+        self.code = []
+        self.repeat_count = 0
+
 def _combine_flags(flags, add_flags, del_flags,
                    TYPE_FLAGS=_parser.TYPE_FLAGS):
     if add_flags & TYPE_FLAGS:
         flags &= ~TYPE_FLAGS
     return (flags | add_flags) & ~del_flags
 
-def _compile(code, pattern, flags):
+def _compile(data, pattern, flags):
     # internal: compile a (sub)pattern
+    code = data.code
     emit = code.append
     _len = len
     LITERAL_CODES = _LITERAL_CODES
@@ -147,15 +154,19 @@ def _compile(code, pattern, flags):
                 skip = _len(code); emit(0)
                 emit(av[0])
                 emit(av[1])
-                _compile(code, av[2], flags)
+                _compile(data, av[2], flags)
                 emit(SUCCESS)
                 code[skip] = _len(code) - skip
             else:
                 emit(REPEATING_CODES[op][0])
                 skip = _len(code); emit(0)
                 emit(av[0])
                 emit(av[1])
-                _compile(code, av[2], flags)
+                # now op is in (MIN_REPEAT, MAX_REPEAT, POSSESSIVE_REPEAT)
+                if op != POSSESSIVE_REPEAT:
+                    emit(data.repeat_count)
+                    data.repeat_count += 1
+                _compile(data, av[2], flags)
                 code[skip] = _len(code) - skip
                 emit(REPEATING_CODES[op][1])
         elif op is SUBPATTERN:
@@ -164,7 +175,7 @@ def _compile(code, pattern, flags):
                 emit(MARK)
                 emit((group-1)*2)
             # _compile_info(code, p, _combine_flags(flags, add_flags, del_flags))
-            _compile(code, p, _combine_flags(flags, add_flags, del_flags))
+            _compile(data, p, _combine_flags(flags, add_flags, del_flags))
             if group:
                 emit(MARK)
                 emit((group-1)*2+1)
@@ -176,7 +187,7 @@ def _compile(code, pattern, flags):
             # pop their stack if they reach it
             emit(ATOMIC_GROUP)
             skip = _len(code); emit(0)
-            _compile(code, av, flags)
+            _compile(data, av, flags)
             emit(SUCCESS)
             code[skip] = _len(code) - skip
         elif op in SUCCESS_CODES:
@@ -191,13 +202,13 @@ def _compile(code, pattern, flags):
                 if lo != hi:
                     raise error("look-behind requires fixed-width pattern")
                 emit(lo) # look behind
-            _compile(code, av[1], flags)
+            _compile(data, av[1], flags)
             emit(SUCCESS)
             code[skip] = _len(code) - skip
         elif op is CALL:
             emit(op)
             skip = _len(code); emit(0)
-            _compile(code, av, flags)
+            _compile(data, av, flags)
             emit(SUCCESS)
             code[skip] = _len(code) - skip
         elif op is AT:
@@ -216,7 +227,7 @@ def _compile(code, pattern, flags):
             for av in av[1]:
                 skip = _len(code); emit(0)
                 # _compile_info(code, av, flags)
-                _compile(code, av, flags)
+                _compile(data, av, flags)
                 emit(JUMP)
                 tailappend(_len(code)); emit(0)
                 code[skip] = _len(code) - skip
@@ -244,12 +255,12 @@ def _compile(code, pattern, flags):
             emit(op)
             emit(av[0]-1)
             skipyes = _len(code); emit(0)
-            _compile(code, av[1], flags)
+            _compile(data, av[1], flags)
             if av[2]:
                 emit(JUMP)
                 skipno = _len(code); emit(0)
                 code[skipyes] = _len(code) - skipyes + 1
-                _compile(code, av[2], flags)
+                _compile(data, av[2], flags)
                 code[skipno] = _len(code) - skipno
             else:
                 code[skipyes] = _len(code) - skipyes + 1
@@ -608,17 +619,17 @@ def isstring(obj):
 def _code(p, flags):
 
     flags = p.state.flags | flags
-    code = []
+    data = _CompileData()
 
     # compile info block
-    _compile_info(code, p, flags)
+    _compile_info(data.code, p, flags)
 
     # compile the pattern
-    _compile(code, p.data, flags)
+    _compile(data, p.data, flags)
 
-    code.append(SUCCESS)
+    data.code.append(SUCCESS)
 
-    return code
+    return data
 
 def _hex_code(code):
     return '[%s]' % ', '.join('%#0*x' % (_sre.CODESIZE*2+2, x) for x in code)
@@ -719,14 +730,21 @@ def print_2(*args):
                     else:
                         print_(FAILURE)
                 i += 1
-            elif op in (REPEAT, REPEAT_ONE, MIN_REPEAT_ONE,
+            elif op in (REPEAT_ONE, MIN_REPEAT_ONE,
                         POSSESSIVE_REPEAT, POSSESSIVE_REPEAT_ONE):
                 skip, min, max = code[i: i+3]
                 if max == MAXREPEAT:
                     max = 'MAXREPEAT'
                 print_(op, skip, min, max, to=i+skip)
                 dis_(i+3, i+skip)
                 i += skip
+            elif op is REPEAT:
+                skip, min, max, repeat_index = code[i: i+4]
+                if max == MAXREPEAT:
+                    max = 'MAXREPEAT'
+                print_(op, skip, min, max, repeat_index, to=i+skip)
+                dis_(i+4, i+skip)
+                i += skip
             elif op is GROUPREF_EXISTS:
                 arg, skip = code[i: i+2]
                 print_(op, arg, skip, to=i+skip)
@@ -781,11 +799,11 @@ def compile(p, flags=0):
     else:
         pattern = None
 
-    code = _code(p, flags)
+    data = _code(p, flags)
 
     if flags & SRE_FLAG_DEBUG:
         print()
-        dis(code)
+        dis(data.code)
 
     # map in either direction
     groupindex = p.state.groupdict
@@ -794,7 +812,6 @@ def compile(p, flags=0):
         indexgroup[i] = k
 
     return _sre.compile(
-        pattern, flags | p.state.flags, code,
-        p.state.groups-1,
-        groupindex, tuple(indexgroup)
-        )
+        pattern, flags | p.state.flags, data.code,
+        p.state.groups-1, groupindex, tuple(indexgroup),
+        data.repeat_count)

Lib/re/_constants.py

@@ -13,7 +13,7 @@
 
 # update when constants are added or removed
 
-MAGIC = 20220318
+MAGIC = 20220402
 
 from _sre import MAXREPEAT, MAXGROUPS
 

Lib/test/test_re.py

@@ -1643,9 +1643,12 @@ def test_dealloc(self):
         long_overflow = 2**128
         self.assertRaises(TypeError, re.finditer, "a", {})
         with self.assertRaises(OverflowError):
-            _sre.compile("abc", 0, [long_overflow], 0, {}, ())
+            _sre.compile("abc", 0, [long_overflow], 0, {}, (), 0)
         with self.assertRaises(TypeError):
-            _sre.compile({}, 0, [], 0, [], [])
+            _sre.compile({}, 0, [], 0, [], [], 0)
+        with self.assertRaises(RuntimeError):
+            # invalid repeat_count -1
+            _sre.compile("abc", 0, [1], 0, {}, (), -1)
 
     def test_search_dot_unicode(self):
         self.assertTrue(re.search("123.*-", '123abc-'))
@@ -2334,6 +2337,27 @@ def test_possesive_repeat(self):
 14. SUCCESS
 ''')
 
+    def test_repeat_index(self):
+        self.assertEqual(get_debug_out(r'(?:ab)*?(?:cd)*'), '''\
+MIN_REPEAT 0 MAXREPEAT
+  LITERAL 97
+  LITERAL 98
+MAX_REPEAT 0 MAXREPEAT
+  LITERAL 99
+  LITERAL 100
+
+ 0. INFO 4 0b0 0 MAXREPEAT (to 5)
+ 5: REPEAT 8 0 MAXREPEAT 0 (to 14)
+10.   LITERAL 0x61 ('a')
+12.   LITERAL 0x62 ('b')
+14: MIN_UNTIL
+15. REPEAT 8 0 MAXREPEAT 1 (to 24)
+20.   LITERAL 0x63 ('c')
+22.   LITERAL 0x64 ('d')
+24: MAX_UNTIL
+25. SUCCESS
+''')
+
 
 class PatternReprTests(unittest.TestCase):
     def check(self, pattern, expected):

Misc/NEWS.d/next/Library/2022-04-03-13-19-08.bpo-23689.TFSc3E.rst

@@ -0,0 +1,2 @@
+:mod:`re` module: fix memory leak when a match is terminated by a signal or
+memory allocation failure. Patch by Ma Lin.