Let's add a fully safe way to exclude certain directories from aging, by
taking a BSD file lock on them before aging them. This is useful for
clients that untar tarballs into /tmp or /var/tmp, which might have
really old timestamps, and to which the aging logic would be very harsh:
they can simply take a BSD file lock on any directory they like and thus
exclude it from automatic aging, and thus need not to be afraid of
untarring stuff below it.
Previously, similar functionality was already available through the
sticky bit on non-directories, but it's problematic, since as soon as
the bit is set no clean-up is done for it at all anymore, forever. Also,
it is not suitable for untarring stuff, since the sticky bit after all
is a concept denoted in the tarball itself. BSD file locking semantics
are much much nicer there, as they are automatically released when the
application that has them dies, and they are entirely orthogonal to data
encoded in tarballs.
This patch takes BSD file locks only on *directories* while descending
down the tree, not on regular files. Moreover, it will do so in
non-blocking mode only, i.e. if anyone else has a lock the aging for a
dir and everything below it is immediately skipped for the current
clean-up iteration.
Of course applications might take BSD file locks for other reasons than
just prevent aging (i.e for their own reasons), but that should be
entirely OK, as in that case tmpfiles should step away from those files
anyway too: it's a good idea to stay away from any such locked file
anyway since it's apparently curretnly being manipulated.
This allows us to fix bugs like this:
https://github.com/systemd/mkosi/issues/252
It would be very wrong if any of the specfier printf calls modified
any of the objects or data being printed. Let's mark all arguments as const
(primarily to make it easier for the reader to see where modifications cannot
occur).
This has the side effect to upgrade the log level at which the log is emitted
from debug to warning.
This might be better since after all we didn't apply a tmpfiles.d/ rule and
that actually might end up being problematic eventually.
and let's emit a more comprehensive warning when an unsafe transition is
encountered.
Before this patch:
Unsafe symlinks encountered in /run/nrpe, refusing.
After:
Detected unsafe path transition / → /run during canonicalization of /run/nrpe.
We previously returned -EPERM but it can be returned for various other reasons
too.
Let's use -ENOLINK instead as this value shouldn't be used currently. This
allows users of CHASE_SAFE to detect without any ambiguities when unsafe
transitions are encountered by chase_symlinks().
All current users of CHASE_SAFE that explicitly reacted on -EPERM have been
converted to react on -ENOLINK.
Ideally, coccinelle would strip unnecessary braces too. But I do not see any
option in coccinelle for this, so instead, I edited the patch text using
search&replace to remove the braces. Unfortunately this is not fully automatic,
in particular it didn't deal well with if-else-if-else blocks and ifdefs, so
there is an increased likelikehood be some bugs in such spots.
I also removed part of the patch that coccinelle generated for udev, where we
returns -1 for failure. This should be fixed independently.
Pretty much everything uses just the first argument, and this doesn't make this
common pattern more complicated, but makes it simpler to pass multiple options.
Previously, we'd always process parents before children. With this
change we are a bit more careful and create parents before children but
clean up children before parents.
The "done" boolean by item is replaced by a mask so that we can descent
and ascend for the right operations only.
See: #9508
This is an implementation that covers making errors encountered when writing
file content optionally fatal. If this is something that folks would want I'll
add handling of this for all the other directives. I'd appreciate suggestions
on how this might better be structured as well (use of a goto fail or such) as
I'm not super happy with the approach.
A follow-up for commit 9d874aec45.
This patch makes "path" parameter mandatory in fd_set_*() helpers removing the
need to use fd_get_path() when NULL was passed. The caller is supposed to pass
the fd anyway so assuming that it also knows the path should be safe.
Actually, the only case where this was useful (or used) was when we were
walking through directory trees (in item_do()). But even in those cases the
paths could be constructed trivially, which is still better than relying on
fd_get_path() (which is an ugly API).
A very succinct test case is also added for 'z/Z' operators so the code dealing
with recursive operators is tested minimally.
Let's fold get_user_creds_clean() into get_user_creds(), and introduce a
flags argument for it to select "clean" behaviour. This flags parameter
also learns to other new flags:
- USER_CREDS_SYNTHESIZE_FALLBACK: in this mode the user records for
root/nobody are only synthesized as fallback. Normally, the synthesized
records take precedence over what is in the user database. With this
flag set this is reversed, and the user database takes precedence, and
the synthesized records are only used if they are missing there. This
flag should be set in cases where doing NSS is deemed safe, and where
there's interest in knowing the correct shell, for example if the
admin changed root's shell to zsh or suchlike.
- USER_CREDS_ALLOW_MISSING: if set, and a UID/GID is specified by
numeric value, and there's no user/group record for it accept it
anyway. This allows us to fix#9767
This then also ports all users to set the most appropriate flags.
Fixes: #9767
[zj: remove one isempty() call]
