linelog: fix infinite loop vulnerability
Checking `len(lines)` is not a great way of detecting infinite loops, as
demonstrated in the added test. Therefore check instruction count instead.
The original C implementation does not have this problem. There are a few
other places where the C implementation enforces more strictly, like
`a1 <= a2`, `b1 <= b2`, `rev > 0`. But they are optional.
Test Plan:
Add a test. The old code forces the test to time out.
Differential Revision: https://phab.mercurial-scm.org/D4151
--- a/mercurial/linelog.py Mon Aug 06 17:19:33 2018 -0400
+++ b/mercurial/linelog.py Mon Aug 06 22:24:00 2018 -0700
@@ -360,13 +360,15 @@
def annotate(self, rev):
pc = 1
lines = []
- # Sanity check: if len(lines) is longer than len(program), we
+ executed = 0
+ # Sanity check: if instructions executed exceeds len(program), we
# hit an infinite loop in the linelog program somehow and we
# should stop.
- while pc is not None and len(lines) < len(self._program):
+ while pc is not None and executed < len(self._program):
inst = self._program[pc]
lastpc = pc
pc = inst.execute(rev, pc, lines.append)
+ executed += 1
if pc is not None:
raise LineLogError(
'Probably hit an infinite loop in linelog. Program:\n' +
--- a/tests/test-linelog.py Mon Aug 06 17:19:33 2018 -0400
+++ b/tests/test-linelog.py Mon Aug 06 22:24:00 2018 -0700
@@ -179,6 +179,15 @@
ar = ll.annotate(rev)
self.assertEqual([(l.rev, l.linenum) for l in ar], lines)
+ def testinfinitebadprogram(self):
+ ll = linelog.linelog.fromdata(
+ b'\x00\x00\x00\x00\x00\x00\x00\x02' # header
+ b'\x00\x00\x00\x00\x00\x00\x00\x01' # JUMP to self
+ )
+ with self.assertRaises(linelog.LineLogError):
+ # should not be an infinite loop and raise
+ ll.annotate(1)
+
if __name__ == '__main__':
import silenttestrunner
silenttestrunner.main(__name__)