Windows device read failure through Python file interface with read buffering enabled

Bug report

Bug description:

Attempting to read the last 16 sectors from a Windows device through the Python file interface fails unexpectedly when buffering is enabled. Those same sectors seem to be accessible without issue through the WIN32 file API itself.

I've included minimal reproduction code. To demonstrate this, configure DEVICE_SECTOR_CNT and DEVICE_PATH to match a drive attached to your system:

import win32file

DEVICE_PATH = "\\\\.\\PhysicalDrive3"
DEVICE_SECTOR_CNT = 62333952
DEVICE_SECTOR_SIZ = 512

for DEVICE_SECTOR_CHK in [DEVICE_SECTOR_CNT - 16, DEVICE_SECTOR_CNT - 15]:

	print("Read sector " + str(DEVICE_SECTOR_CHK) + " through win32file:")
	try:
		handle = win32file.CreateFile(
			DEVICE_PATH,
			win32file.GENERIC_READ | win32file.GENERIC_WRITE,
			win32file.FILE_SHARE_READ | win32file.FILE_SHARE_WRITE,
			None,
			win32file.OPEN_EXISTING,
			0,
			None
		)
		win32file.SetFilePointer(handle, DEVICE_SECTOR_CHK * DEVICE_SECTOR_SIZ, win32file.FILE_BEGIN)
		(_, result) = win32file.ReadFile(handle, DEVICE_SECTOR_SIZ)
		print(" ".join(["{:02X}".format(x) for x in result]))
	finally:
		win32file.CloseHandle(handle)

	print("Read sector " + str(DEVICE_SECTOR_CHK) + " through open:")
	with open(DEVICE_PATH, "rb") as device:
		device.seek(DEVICE_SECTOR_CHK * DEVICE_SECTOR_SIZ)
		result = device.read(DEVICE_SECTOR_SIZ)
		print(" ".join(["{:02X}".format(x) for x in result]))

Testing this with any drive attached to my system, I see a result like:

Read sector 62333936 through win32file:
FD FF F3 FF FB FF F3 FF F9 FF F8 FF FF FF FB FF 01 00 01 00 03 00 02 00 07 00 05 00 09 00 02 00 06 00 03 00 04 00 02 00 08 00 06 00 0C 00 08 00 0D 00 07 00 0B 00 07 00 0B 00 04 00 0E 00 05 00 0D 00 04 00 0C 00 06 00 0B 00 07 00 0C 00 08 00 0D 00 07 00 0D 00 07 00 0D 00 08 00 0B 00 05 00 0B 00 04 00 0F 00 06 00 13 00 0C 00 15 00 10 00 16 00 0F 00 14 00 0E 00 14 00 0F 00 16 00 0E 00 16 00 0F 00 17 00 10 00 15 00 10 00 11 00 0F 00 13 00 0A 00 14 00 06 00 13 00 09 00 12 00 0C 00 15 00 08 00 11 00 06 00 13 00 06 00 14 00 0A 00 12 00 0D 00 14 00 0A 00 0E 00 07 00 0F 00 04 00 11 00 06 00 0F 00 08 00 0D 00 0C 00 0D 00 0A 00 0F 00 03 00 0D 00 FF FF 0B 00 FD FF 09 00 FF FF 08 00 04 00 07 00 01 00 0A 00 00 00 0C 00 FD FF 0B 00 FC FF 06 00 FE FF 02 00 FD FF 01 00 FC FF 06 00 FD FF 09 00 FA FF 06 00 FD FF 04 00 FF FF 01 00 F9 FF FE FF FC FF FF FF F8 FF 02 00 F7 FF 01 00 F7 FF FE FF FA FF FE FF F6 FF FD FF F5 FF FD FF F5 FF FB FF F5 FF FC FF F4 FF FC FF FA FF FC FF FB FF FF FF FD FF FE FF FA FF 03 00 FE FF 04 00 FD FF FD FF FD FF 01 00 FC FF 02 00 FE FF 01 00 FC FF 02 00 F8 FF 00 00 F7 FF FF FF FB FF 00 00 FB FF 01 00 F5 FF FE FF F7 FF FD FF FA FF FE FF F9 FF 00 00 F7 FF FF FF F8 FF FF FF F9 FF 01 00 F3 FF 00 00 F5 FF FE FF F7 FF FF FF F5 FF FF FF F7 FF 01 00 FD FF 00 00 FA FF FC FF F5 FF F9 FF F3 FF FB FF F2 FF FC FF F3 FF FE FF F9 FF 01 00 FD FF FE FF FE FF FF FF F4 FF FF FF F0 FF FC FF F1 FF FF FF F8 FF 03 00 04 00 04 00 03 00 06 00 FD FF 04 00 F6 FF FC FF F5 FF F8 FF F5 FF F9 FF F9 FF FC FF FD FF 02 00 FB FF 05 00 FA FF
Read sector 62333936 through open:
FD FF F3 FF FB FF F3 FF F9 FF F8 FF FF FF FB FF 01 00 01 00 03 00 02 00 07 00 05 00 09 00 02 00 06 00 03 00 04 00 02 00 08 00 06 00 0C 00 08 00 0D 00 07 00 0B 00 07 00 0B 00 04 00 0E 00 05 00 0D 00 04 00 0C 00 06 00 0B 00 07 00 0C 00 08 00 0D 00 07 00 0D 00 07 00 0D 00 08 00 0B 00 05 00 0B 00 04 00 0F 00 06 00 13 00 0C 00 15 00 10 00 16 00 0F 00 14 00 0E 00 14 00 0F 00 16 00 0E 00 16 00 0F 00 17 00 10 00 15 00 10 00 11 00 0F 00 13 00 0A 00 14 00 06 00 13 00 09 00 12 00 0C 00 15 00 08 00 11 00 06 00 13 00 06 00 14 00 0A 00 12 00 0D 00 14 00 0A 00 0E 00 07 00 0F 00 04 00 11 00 06 00 0F 00 08 00 0D 00 0C 00 0D 00 0A 00 0F 00 03 00 0D 00 FF FF 0B 00 FD FF 09 00 FF FF 08 00 04 00 07 00 01 00 0A 00 00 00 0C 00 FD FF 0B 00 FC FF 06 00 FE FF 02 00 FD FF 01 00 FC FF 06 00 FD FF 09 00 FA FF 06 00 FD FF 04 00 FF FF 01 00 F9 FF FE FF FC FF FF FF F8 FF 02 00 F7 FF 01 00 F7 FF FE FF FA FF FE FF F6 FF FD FF F5 FF FD FF F5 FF FB FF F5 FF FC FF F4 FF FC FF FA FF FC FF FB FF FF FF FD FF FE FF FA FF 03 00 FE FF 04 00 FD FF FD FF FD FF 01 00 FC FF 02 00 FE FF 01 00 FC FF 02 00 F8 FF 00 00 F7 FF FF FF FB FF 00 00 FB FF 01 00 F5 FF FE FF F7 FF FD FF FA FF FE FF F9 FF 00 00 F7 FF FF FF F8 FF FF FF F9 FF 01 00 F3 FF 00 00 F5 FF FE FF F7 FF FF FF F5 FF FF FF F7 FF 01 00 FD FF 00 00 FA FF FC FF F5 FF F9 FF F3 FF FB FF F2 FF FC FF F3 FF FE FF F9 FF 01 00 FD FF FE FF FE FF FF FF F4 FF FF FF F0 FF FC FF F1 FF FF FF F8 FF 03 00 04 00 04 00 03 00 06 00 FD FF 04 00 F6 FF FC FF F5 FF F8 FF F5 FF F9 FF F9 FF FC FF FD FF 02 00 FB FF 05 00 FA FF
Read sector 62333937 through win32file:
FF FF FD FF 01 00 FC FF 01 00 FA FF FE FF F6 FF 02 00 F5 FF 06 00 F7 FF 03 00 FD FF 00 00 03 00 00 00 00 00 04 00 FA FF 07 00 F9 FF 05 00 F7 FF 00 00 FB FF FC FF FD FF 00 00 FC FF 04 00 FB FF 04 00 FB FF 02 00 FF FF 01 00 F9 FF FE FF F4 FF BF 75 03 00 EB B2 11 00 C0 31 2D 67 00 06 00 00 FF FF F2 FF 02 00 F2 FF 03 00 F7 FF 01 00 FB FF FB FF F4 FF FA FF F4 FF F8 FF ED FF F7 FF E8 FF F5 FF F0 FF F6 FF F4 FF F7 FF F9 FF F9 FF F6 FF FF FF F6 FF FF FF F7 FF FC FF F5 FF FA FF F5 FF F7 FF F6 FF FC FF F4 FF FF FF FA FF FE FF FC FF FC FF FD FF FC FF F8 FF F8 FF F3 FF F6 FF EE FF F3 FF EE FF F6 FF F4 FF F6 FF F6 FF FB FF F7 FF FF FF F8 FF FF FF F6 FF FC FF F5 FF F9 FF F5 FF F8 FF F3 FF F6 FF F4 FF FA FF F7 FF FC FF F8 FF FA FF FC FF FE FF FB FF FC FF F6 FF FA FF F4 FF FB FF F2 FF FA FF F3 FF FE FF F5 FF F9 FF FC FF F8 FF FB FF FA FF F4 FF FC FF F7 FF FF FF F5 FF FB FF F8 FF F9 FF F6 FF F7 FF F6 FF F9 FF F3 FF F9 FF F1 FF FA FF F4 FF FA FF F8 FF F6 FF FA FF F6 FF F4 FF F5 FF F1 FF F9 FF F3 FF FB FF F6 FF F6 FF F6 FF F5 FF F6 FF FC FF F9 FF 00 00 F4 FF FC FF F4 FF FD FF F7 FF FD FF F9 FF 01 00 FA FF FF FF FE FF 00 00 FE FF 01 00 02 00 03 00 03 00 03 00 FE FF 05 00 FF FF 05 00 04 00 09 00 0A 00 0C 00 0F 00 0B 00 10 00 0F 00 0D 00 12 00 09 00 11 00 0A 00 11 00 0B 00 0D 00 12 00 11 00 16 00 15 00 15 00 18 00 19 00 19 00 18 00 14 00 18 00 11 00 16 00 12 00 14 00 13 00 15 00 17 00 1C 00 17 00 20 00 1A 00 1F 00 1D 00 1C 00 1A 00 16 00 16 00 14 00 11 00 11 00 11 00 15 00 14 00 1F 00 19 00 1E 00 1B 00 1C 00 15 00 17 00 17 00 16 00
Read sector 62333937 through open:
Traceback (most recent call last):
  File "...", line 29, in <module>
    result = device.read(DEVICE_SECTOR_SIZ)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
PermissionError: [Errno 13] Permission denied

Note that when I see this, the generated Errno is different for different devices. This could possibly be a bug in some Windows API that Python is relying on, but I'm not the one to determine that. If buffering is disabled in the Python file interface (by adding , 0 to the end of the open(...) call) then this issue does not occur, so my immediate suspicion is that the buffer implementation is reading past the end of the device for some reason.

This has been tested with Python 3.12.3 on Windows 11 10.0.22631

CPython versions tested on:

3.12

Operating systems tested on:

Windows

从 Windows 11 上使用 Python 3.12.3 的最小复现开始，比较带缓冲的 open(...).read()、禁用缓冲的情况以及 win32file 路径。完成的标准是，带缓冲的 Python 文件接口在读取设备的最后几个扇区时不再失败，并且该行为由适当的回归测试覆盖。