ensure internal buffer is large enough for string after flushing (closes #24481)

Lib/test/test_hotshot.py

@@ -149,6 +149,10 @@ class HotShotTestCase(unittest.TestCase):
         stats.load(self.logfn)
         os.unlink(self.logfn)
 
+    def test_large_info(self):
+        p = self.new_profiler()
+        self.assertRaises(ValueError, p.addinfo, "A", "A" * 0xfceb)
+
 
 def test_main():
     test_support.run_unittest(HotShotTestCase)

Misc/NEWS

@@ -30,6 +30,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #24481: Fix possible memory corruption with large profiler info strings
+  in hotshot.
+
 - Issue #24489: ensure a previously set C errno doesn't disturb cmath.polar().
 
 - Issue #19543: io.TextIOWrapper (and hence io.open()) now uses the internal

Modules/_hotshot.c

@@ -626,6 +626,10 @@ pack_string(ProfilerObject *self, const char *s, Py_ssize_t len)
     if (len + PISIZE + self->index >= BUFFERSIZE) {
         if (flush_data(self) < 0)
             return -1;
+        if (len + PISIZE + self->index >= BUFFERSIZE) {
+            PyErr_SetString(PyExc_ValueError, "string too large for internal buffer");
+            return -1;
+        }
     }
     assert(len < INT_MAX);
     if (pack_packed_int(self, (int)len) < 0)