gh-140607: Validate returned byte count in RawIOBase.read (#140611)

While `RawIOBase.readinto` should return a count of bytes between 0 and
the length of the given buffer, it is not required to. Add validation
inside RawIOBase.read() that the returned byte count is valid.

Co-authored-by: Shamil <ashm.tech@proton.me>
Co-authored-by: Victor Stinner <vstinner@python.org>

Lib/_pyio.py

@@ -617,6 +617,8 @@ def read(self, size=-1):
         n = self.readinto(b)
         if n is None:
             return None
+        if n < 0 or n > len(b):
+            raise ValueError(f"readinto returned {n} outside buffer size {len(b)}")
         del b[n:]
         return bytes(b)