internal/poll: invalid uintptr conversion in call to windows.SetFileInformationByHandle

[gopherbot]

#!watchflakes
post <- pkg == "os" && test == "TestChmod" && `The parameter is incorrect`

Issue created automatically to collect these failures.

Example (log):

--- FAIL: TestChmod (0.00s)
    os_test.go:1278: chmod C:\Users\gopher\AppData\Local\Temp\1\_Go_TestChmod2722485006 0666: chmod C:\Users\gopher\AppData\Local\Temp\1\_Go_TestChmod2722485006: The parameter is incorrect.

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
post <- pkg == "os" && test == "TestChmod"

2023-03-07 22:05 windows-amd64-race go@99914db5 os.TestChmod (log)

--- FAIL: TestChmod (0.00s)
    os_test.go:1278: chmod C:\Users\gopher\AppData\Local\Temp\1\_Go_TestChmod2722485006 0666: chmod C:\Users\gopher\AppData\Local\Temp\1\_Go_TestChmod2722485006: The parameter is incorrect.

— watchflakes

[bcmills]

(CC @golang/windows)

[bcmills]

This test was enabled on Windows in CL 250077 for #39606 (CC @iwdgo), and I marked it as safe to run in parallel in CL 458015.

It's not at all clear to me why it would fail nondeterministically, although it's curious that the one failure reported here is on the -race builder. 🤔

[alexbrainman]

I just looked at the internal/poll.FD.Fchmod code again, and it does not look right to me. For example, why do we only set du.FileAttributes and not du.CreationTime and other fields here?

go/src/internal/poll/fd_windows.go

Lines 1027 to 1030 in 618fb4a

	var du windows.FILE_BASIC_INFO
	du.FileAttributes = attrs
	l := uint32(unsafe.Sizeof(d))
	return windows.SetFileInformationByHandle(fd.Sysfd, windows.FileBasicInfo, uintptr(unsafe.Pointer(&du)), l)

Our code appears to set CreationTime (and all time related fields) to 0. This is wrong. No?

We should extend os.TestChmod to compare file times before and after os.Chmod call.

Alex.

[gopherbot]

Change https://go.dev/cl/490855 mentions this issue: os: set actual length of structure passed to SetFileInformationByHandle

[qmuntal]

I just looked at the internal/poll.FD.Fchmod code again, and it does not look right to me. For example, why do we only set du.FileAttributes and not du.CreationTime and other fields here?

FILE_BASIC_INFO does not document what happens when time fields are set to 0, but SetFileInformationByHandle calls NtSetInformationFile under the hood, which casts the basic info into FILE_BASIC_INFORMATION. This last struct does document what happens in this situation:

If you specify a value of zero for any of the XxxTime members of the FILE_BASIC_INFORMATION structure, the ZwSetInformationFile function keeps a file's current setting for that time.

We should extend os.TestChmod to compare file times before and after os.Chmod call.

Agree. If we rely on an undocumented behavior then we should at least test our assumptions.

[bcmills]

Just saw one of these on a windows/386 LUCI TryBot:
https://ci.chromium.org/ui/p/golang/builders/try-workers/gotip-windows-386-test_only/b8761882490968913201/test-results?sortby=&groupby=

=== RUN   TestChmod
=== PAUSE TestChmod
=== CONT  TestChmod
    os_test.go:1294: chmod C:\b\s\w\ir\x\t\_Go_TestChmod1719170795 0666: chmod C:\b\s\w\ir\x\t\_Go_TestChmod1719170795: The parameter is incorrect.
--- FAIL: TestChmod (0.01s)

[bcmills]

Oh, yeah, here's a bug, at least:
https://cs.opensource.google/go/go/+/master:src/internal/syscall/windows/syscall_windows.go;l=153;drc=693def151adff1af707d82d28f55dba81ceb08e1

The third argument violates the unsafe.Pointer rules by passing a pointer to a Go object as type uintptr.

That can cause the buffer to be garbage-collected and reused while the call is in progress, leading to arbitrary corruption of its contents.

[gopherbot]

Change https://go.dev/cl/549256 mentions this issue: internal/syscall/windows: fix the signature of SetFileInformationByHandle

[bcmills]

@gopherbot, please backport to Go 1.21. This was a use-after-free bug and could cause arbitrary heap corruption in programs that call SetFileInformationByHandle, and it also produces nondeterministic test failures on the release-branch.go1.21 builders.

[gopherbot]

Backport issue(s) opened: #65882 (for 1.21).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.

[gopherbot]

Change https://go.dev/cl/566155 mentions this issue: [release-branch.go1.21] internal/syscall/windows: fix the signature of SetFileInformationByHandle