machine: ensure disk image is writable before resize (fix read-only image init failure)

[jude-ruben]

Problem

Initializing a Podman machine with a read-only disk image (e.g., chmod 444)
fails during the resize step with a permission denied error.

Root Cause

The disk image created from user input may retain read-only permissions.
The resize operation (qemu-img) requires write access but no step ensures
the image is writable before resizing.

Solution

Ensure the disk image is set to writable (0600) before resize operations
using os.Chmod.

Test

Added an e2e test:

• Copy a valid image
• Make it read-only (chmod 444)
• Run podman machine init
• Verify success

Result

• Before: resize fails with permission denied
• After: machine initializes successfully

Fixes #27576

[baude]

would like it if you made this error message slightly different so anyone debugging could tell which path immediately they are on? so maybe failed to set permissions on pulled image %s ?

[jude-ruben]

can you check now @baude

[baude]

did you confirm that any of the other providers also have this problem?

[baude]

maybe using install here is more efficient?

[jude-ruben]

can you check now @baude

[jude-ruben]

did you confirm that any of the other providers also have this problem?

@baude ,I verified this behavior only occurs for the QEMU provider. The pulled image is resized during machine init for QEMU, which requires write permissions. Other providers do not resize the pulled image in the same way, so they are not affected.

[ashley-cui]

please run make validate or make validatepr locally before you re-push with your changes; this should help with the linter errors.

[Honny1]

Hello @jude-ruben, please rebase on the upstream main branch. We changed import paths recently.
Also please resolve linting issue:

+ ./bin/golangci-lint run --build-tags=apparmor,seccomp,selinux
pkg/machine/e2e/init_test.go:743:62: Error return value of `(*os/exec.Cmd).Run` is not checked (errcheck)
		exec.Command("install", "-m", "444", mb.imagePath, img).Run()
		                                                           ^
pkg/machine/e2e/init_test.go:749:3: ginkgo-linter: wrong error assertion. Consider using `Expect(err).ToNot(HaveOccurred())` instead (ginkgolinter)
		Expect(err).To(BeNil())
		^
pkg/machine/stdpull/local.go:37:1: File is not properly formatted (gofumpt)
	if err := os.Chmod(s.finalPath.GetPath(), 0600); err != nil {
^
pkg/machine/stdpull/url.go:84:1: File is not properly formatted (gofumpt)
	if err := os.Chmod(d.finalPath.GetPath(), 0600); err != nil {
^
pkg/machine/stdpull/local.go:42:1: unnecessary trailing newline (whitespace)
}
^

Thanks.