linux: build hardened kernel with matching releases

Until now we merged kernel updates even if no hardened versions were
available yet. On one hand we don't want to delay patch-level updates,
on the other hand users of hardened kernels have frequent breakage now[1].

This change aims to provide a solution this issue:

* The hardened patchset now references the kernel version it's released
  for (including a sha256 hash for the fixed-output path of the source
  tarball).
* The `hardenedKernelFor`-function doesn't just append hardened patches
  now, but also overrides version & src to match the kernel version the
  patch was built & tested for.

Refs #140281

[1] https://hydra.nixos.org/job/nixos/trunk-combined/nixpkgs.linuxPackages_hardened.kernel.x86_64-linux/all

(cherry picked from commit bb5aa0109b6db98a2e0a7ba88f5e0287e2374384)

pkgs/os-specific/linux/kernel/hardened/update.py

@@ -31,7 +31,12 @@ VersionComponent = Union[int, str]
 Version = List[VersionComponent]
 
 
-Patch = TypedDict("Patch", {"name": str, "url": str, "sha256": str, "extra": str})
+PatchData = TypedDict("PatchData", {"name": str, "url": str, "sha256": str, "extra": str})
+Patch = TypedDict("Patch", {
+    "patch": PatchData,
+    "version": str,
+    "sha256": str,
+})
 
 
 @dataclass
@@ -133,7 +138,15 @@ def fetch_patch(*, name: str, release_info: ReleaseInfo) -> Optional[Patch]:
     if not sig_ok:
         return None
 
-    return Patch(name=patch_filename, url=patch_url, sha256=sha256, extra=extra)
+    kernel_ver = release_info.release.tag_name.replace("-hardened1", "")
+    major = kernel_ver.split('.')[0]
+    sha256_kernel, _ = nix_prefetch_url(f"mirror://kernel/linux/kernel/v{major}.x/linux-{kernel_ver}.tar.xz")
+
+    return Patch(
+        patch=PatchData(name=patch_filename, url=patch_url, sha256=sha256, extra=extra),
+        version=kernel_ver,
+        sha256=sha256_kernel
+    )
 
 
 def parse_version(version_str: str) -> Version:
@@ -245,7 +258,7 @@ for kernel_key in sorted(releases.keys()):
     old_version_str: Optional[str] = None
     update: bool
     try:
-        old_filename = patches[kernel_key]["name"]
+        old_filename = patches[kernel_key]["patch"]["name"]
         old_version_str = old_filename.replace("linux-hardened-", "").replace(
             ".patch", ""
         )