chase_symlinks() would return negative on error, and either a non-negative status
or a non-negative fd when CHASE_OPEN was given. This made the interface quite
complicated, because dependning on the flags used, we would get two different
"types" of return object. Coverity was always confused by this, and flagged
every use of chase_symlinks() without CHASE_OPEN as a resource leak (because it
would this that an fd is returned). This patch uses a saparate output parameter,
so there is no confusion.
(I think it is OK to have functions which return either an error or an fd. It's
only returning *either* an fd or a non-fd that is confusing.)
This reverts commit b26c904113.
I don't see anythign wrong, but Ubuntu autopkgtest CI started failing fairly
consistently since this was merged. Let's see if reverting fixes things.
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.
This splits out a bunch of functions from fileio.c that have to do with
temporary files. Simply to make the header files a bit shorter, and to
group things more nicely.
No code changes, just some rearranging of source files.
This removes $RENAME_NOREPLACE_DIR and uses a command-line argument instead.
Logging is added, and tests are skipped if we get -EPERM or friends
(which happens on FAT and other filesystems).
This flag mimics what "O_NOFOLLOW|O_PATH" does for open(2) that is
chase_symlinks() will not resolve the final pathname component if it's a
symlink and instead will return a file descriptor referring to the symlink
itself.
Note: if CHASE_SAFE is also passed, no safety checking is performed on the
transition done if the symlink would have been followed.
These lines are generally out-of-date, incomplete and unnecessary. With
SPDX and git repository much more accurate and fine grained information
about licensing and authorship is available, hence let's drop the
per-file copyright notice. Of course, removing copyright lines of others
is problematic, hence this commit only removes my own lines and leaves
all others untouched. It might be nicer if sooner or later those could
go away too, making git the only and accurate source of authorship
information.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
If the flag is set only a single step of the normalization is executed,
and the resulting path is returned.
This allows callers to normalize piecemeal, taking into account every
single intermediary path of the normalization.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
We have the same code for this in place at various locations, let's
unify that. Also, let's repurpose test-fs-util.c as a test for this new
helper cal..
When we are attempting to create directory somewhere in the bowels of /var/lib
and get an error that it already exists, it can be quite hard to diagnose what
is wrong (especially for a user who is not aware that the directory must have
the specified owner, and permissions not looser than what was requested). Let's
print a warning in most cases. A warning is appropriate, because such state is
usually a sign of borked installation and needs to be resolved by the adminstrator.
$ build/test-fs-util
Path "/tmp/test-readlink_and_make_absolute" already exists and is not a directory, refusing.
(or)
Directory "/tmp/test-readlink_and_make_absolute" already exists, but has mode 0775 that is too permissive (0755 was requested), refusing.
(or)
Directory "/tmp/test-readlink_and_make_absolute" already exists, but is owned by 1001:1000 (1000:1000 was requested), refusing.
Assertion 'mkdir_safe(tempdir, 0755, getuid(), getgid(), MKDIR_WARN_MODE) >= 0' failed at ../src/test/test-fs-util.c:320, function test_readlink_and_make_absolute(). Aborting.
No functional change except for the new log lines.
This new helper not only removes a file from a directory but also
ensures its space on disk is deallocated, by either punching a hole over
the full file or truncating the file afterwards if the file's link
counter is 0. This is useful in "vacuuming" algorithms to ensure that
client's can't keep the disk space the vacuuming is supposed to recover
pinned simply by keeping an fd open to it.
The new flag returns the O_PATH fd of the final component, which may be
converted into a proper fd by open()ing it again through the
/proc/self/fd/xyz path.
Together with O_SAFE this provides us with a somewhat safe way to open()
files in directories potentially owned by unprivileged code, where we
want to refuse operation if any symlink tricks are played pointing to
privileged files.
When the flag is specified we won't transition to a privilege-owned
file or directory from an unprivileged-owned one. This is useful when
privileged code wants to load data from a file unprivileged users have
write access to, and validates the ownership, but want's to make sure
that no symlink games are played to read a root-owned system file
belonging to a different context.
Let's rework touch_file() so that it works correctly on sockets, fifos,
and device nodes: let's open an O_PATH file descriptor first and operate
based on that, if we can. This is usually the better option as it this
means we can open AF_UNIX nodes in the file system, and update their
timestamps and ownership correctly. It also means we can correctly touch
symlinks and block/character devices without triggering their drivers.
Moreover, by operating on an O_PATH fd we can make sure that we
operate on the same inode the whole time, and it can't be swapped out in
the middle.
While we are at it, rework the call so that we try to adjust as much as
we can before returning on error. This is a good idea as we call the
function quite often without checking its result, and hence it's best to
leave the files around in the most "correct" fashion possible.
The kernel will reply with -ENOTDIR when we try to access a non-directory under
a name which ends with a slash. But our functions would strip the trailing slash
under various circumstances. Keep the trailing slash, so that
path_is_mount_point("/path/to/file/") return -ENOTDIR when /path/to/file/ is a file.
Tests are added for this change in behaviour.
Also, when called with a trailing slash, path_is_mount_point() would get
"" from basename(), and call name_to_handle_at(3, "", ...), and always
return -ENOENT. Now it'll return -ENOTDIR if the mount point is a file, and
true if it is a directory and a mount point.
v2:
- use strip_trailing_chars()
v3:
- instead of stripping trailing chars(), do the opposite — preserve them.
Linux doesn't have faccess(), hence let's emulate it. Linux has access()
and faccessat() but neither allows checking the access rights of an fd
passed in directly.
test_readlink_and_make_absolute switches to a temp directory, and then
removes it.
test_get_files_in_directory calls opendir(".") from a directory that has
been removed from the filesystem.
This call sequence triggers a bug in Gentoo's sandbox library. This
library attempts to resolve the "." to an absolute path, and aborts when
it ultimately fails to do so.
Re-ordering the calls works around the issue until the sandbox library
can be fixed to more gracefully deal with this.
Bug: https://bugs.gentoo.org/590084
If chase_symlinks() encouters an absolute symlink, it resets the todo
buffer to just the newly discovered symlink and discards any of the
remaining previous symlink path. Regardless of whether or not the
symlink is absolute or relative, we need to preserve the remainder of
the path that has not yet been resolved.
Fixes:
```
$ ./libtool --mode=execute valgrind --leak-check=full ./test-fs-util
...
==22871==
==22871== 27 bytes in 1 blocks are definitely lost in loss record 1 of 1
==22871== at 0x4C2FC47: realloc (vg_replace_malloc.c:785)
==22871== by 0x4E86D05: strextend (string-util.c:726)
==22871== by 0x4E8F347: chase_symlinks (fs-util.c:712)
==22871== by 0x109EBF: test_chase_symlinks (test-fs-util.c:75)
==22871== by 0x10C381: main (test-fs-util.c:305)
==22871==
```
Closes#4888
This new flag controls whether to consider a problem if the referenced path
doesn't actually exist. If specified it's OK if the final file doesn't exist.
Note that this permits one or more final components of the path not to exist,
but these must not contain "../" for safety reasons (or, to be extra safe,
neither "./" and a couple of others, i.e. what path_is_safe() permits).
This new flag is useful when resolving paths before issuing an mkdir() or
open(O_CREAT) on a path, as it permits that the file or directory is created
later.
The return code of chase_symlinks() is changed to return 1 if the file exists,
and 0 if it doesn't. The latter is only returned in case CHASE_NON_EXISTING is
set.
Let's remove chase_symlinks_prefix() and instead introduce a flags parameter to
chase_symlinks(), with a flag CHASE_PREFIX_ROOT that exposes the behaviour of
chase_symlinks_prefix().