We can get rid of `NarMember`, because it is just `NarListing` in
disguise! The use of `std::variant` makes clear that certain stat fields
we don't care about in the non-regular-file case too.
Relative paths (e.g., "relative/repo") would crash in renderAuthorityAndPath()
because an empty authority was set, violating RFC 3986 section 3.3 which
requires paths to start with "/" when an authority is present.
Fix by only setting authority for absolute paths:
- Absolute paths: file:///path (empty authority)
- Relative paths: file:path (no authority)
Also reject SCP-like URLs without a user (e.g., "github.com:path") with a
clear error message, since proper support requires careful implementation,
which is not something I can do right now.
Relative paths like `file:./foo.tar.gz` have never worked for tarballs
because curl rejects relative file: URLs. Previously this resulted in
cryptic curl errors. Now we reject them early with a clear message
explaining that relative paths are not supported because there is no
defined base directory to resolve them against.
See https://github.com/NixOS/nix/issues/12281
When a goal with an active child process is destroyed (e.g., during
failure cascades without `--keep-going`), the child process gets killed
but `childTerminated` was never called. This left stale entries in the
worker's `children` list.
Fix this by ensuring `childTerminated` is called from destructors:
- `DerivationBuilderImpl::killChild` now calls `childTerminated` via
the `miscMethods` callback.
- `HookInstance` gains an `onKillChild` callback that is invoked from
its destructor when killing the process. `buildWithHook` sets this
callback to call `childTerminated`.
To make these calls safe from destructors (where the goal object may be
partially destroyed), add a new overload of `Worker::childTerminated`
that takes an explicit `JobCategory` parameter instead of calling the
virtual method `Goal::jobCategory`. The original overload still exists
for convenience for normal (non-destructor) call sites.
It correctly models the is-a relation. This will be useful for doing a dynamic_cast in
downstream code that wants to copy from a file descriptor to a file descriptor.
This also adds a utility for opening a file descriptor from a path in readonly mode.
Previous commit helps a bit with error handling, since now we just throw a NativeSysError.
This way each consumer of NativeSysError doesn't have to
also conditionally include the windows-error.hh, which is very cumbersome.
And we can't include windows-error.hh in error.hh because of a circular import.
Previously builtins.readDir would return an empty attribute set
instead of barfing on non-existent paths. This is a regression from
2.32 for impure eval.
Using fchmodat after a fstatat in deletePath has a slight TOCTOU
window. We can plug it by using fchmodat (the libc wrapper with
AT_SYMLINK_NOFOLLOW), but it tries fchmodat2 and falls back to the
O_PATH trick while failing when procfs isn't mounted. We can do a bit
better than that and also cache whether syscalls are unsupported to
avoid the repeated context switching that glibc would impose.
Also tests the fallback path. It's only for kernels older than 6.6 and
when procfs isn't accessible that we fall back to the racy fchmodat
without AT_SYMLINK_NOFOLLOW.
What previously used to be:
openat(AT_FDCWD, "/tmp/store-race/nix/var/nix/builds", O_RDONLY) = 11
newfstatat(11, "nix-2704212-84654554", {st_mode=S_IFDIR|000, st_size=3, ...}, AT_SYMLINK_NOFOLLOW) = 0
fchmodat(11, "nix-2704212-84654554", 040700) = 0
Is now a TOCTOU-free sequence of syscalls:
openat(AT_FDCWD, "/tmp/store-race/nix/var/nix/builds", O_RDONLY) = 11
newfstatat(11, "nix-2704953-1733606057", {st_mode=S_IFDIR|000, st_size=3, ...}, AT_SYMLINK_NOFOLLOW) = 0
fchmodat2(11, "nix-2704953-1733606057", 040700, AT_SYMLINK_NOFOLLOW) = 0
Or if the fchmodat2 is not supported:
openat(11, "nix-2705443-3010460784", O_RDONLY|O_NOFOLLOW|O_CLOEXEC|O_PATH) = 12
fstat(12, {st_mode=S_IFDIR|000, st_size=3, ...}) = 0
chmod("/proc/self/fd/12", 040700) = 0
openat(11, "nix-2705443-3010460784", O_RDONLY|O_NOFOLLOW|O_DIRECTORY) = 12
This prevents a potentially arbitrary chmod that follows symlinks,
though the race window is very small. Also in the case that fchmodat2
isn't supported we could instead open the /proc/self/fd/N path instead
of using openat, but that's pretty much equivalent. We only care
about ensuring that the thing we chmodded wasn't a symlink since
fchmodat follows symlinks and the support for AT_SYMLINK_NOFOLLOW
in libc for that is pretty spotty on Linux. E.g. glibc fails if the
AT_SYMLINK_NOFOLLOW is specified and procfs isn't available even on
regular files. The patch also includes a test that uses a user namespace
on Linux to test this exact scenario (though it's rather exotic).
