Prakash Surya
0b58f1db89
When the path argument to "zfs list -Ho name <path>" (or any caller of
zfs_path_to_zhandle()) is a symlink that crosses a mount boundary, the
wrong dataset is returned. Instead of returning the dataset that owns
the symlink's target, getextmntent() matches the dataset containing the
symlink itself.
For example, given two ZFS datasets "tank/ds1" and "tank/ds2", and a
symlink "/tank/ds1/link" pointing into "/tank/ds2":
$ sudo zfs list -Ho name /tank/ds1/link
tank/ds1
The expected (and previous) behavior is to return "tank/ds2", since the
symlink's target resides in that dataset.
The problem is in getextmntent(), in lib/libspl/os/linux/mnttab.c. That
function calls statx() on the caller-supplied path to obtain its mnt_id
(used to match against the mnt_id of each entry in /proc/self/mounts),
and it passes AT_SYMLINK_NOFOLLOW to that statx() call. As a result,
the mnt_id returned reflects the symlink's location rather than the
symlink target's mount, and the wrong /proc/self/mounts entry is
matched.
The same function also calls stat64() on the caller-supplied path
(used as a fallback when STATX_MNT_ID is not available, and to populate
the statbuf out-parameter). stat64() always follows symlinks, so the
statx() and stat64() calls were inconsistent: one resolved the symlink,
the other didn't. The AT_SYMLINK_NOFOLLOW behavior may be appropriate
when statx() is called on a mount entry from /proc/self/mounts (which
is always a real directory), but it is wrong for caller-supplied paths,
which may be symlinks.
This bug was introduced by 523d9d6007 ("Validate mountpoint on
path-based unmount using statx"), which added the STATX_MNT_ID code
path. However, the bug was latent: config/user-statx.m4 omitted
"#define _GNU_SOURCE" when checking for STATX_MNT_ID in <sys/stat.h>,
so HAVE_STATX_MNT_ID was never defined, and the buggy statx() path was
never compiled in. getextmntent() always fell back to the dev_t
comparison via stat64(), which correctly follows symlinks.
The fix to that autoconf check, in 2b930f63f8 ("config: fix
STATX_MNT_ID detection"), caused HAVE_STATX_MNT_ID to be properly
defined on kernels that support it, activating the broken
AT_SYMLINK_NOFOLLOW path for the first time and exposing the
regression.
The fix is to drop AT_SYMLINK_NOFOLLOW from the statx() call so that
symlinks are followed, matching the behavior of stat64() on the same
path.
Verified with a minimal reproducer: created two ZFS datasets, placed a
symlink inside the first pointing into the second, and confirmed that
"zfs list -Ho name <symlink>" returns the dataset containing the
symlink's target rather than the dataset containing the symlink.
Signed-off-by: Prakash Surya <prakash.surya@perforce.com>
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.
Official Resources
- Documentation - for using and developing this repo
- ZoL site - Linux release info & links
- Mailing lists
- OpenZFS site - for conference videos and info on other platforms (illumos, OSX, Windows, etc)
Installation
Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.
Contribute & Develop
We have a separate document with contribution guidelines.
We have a Code of Conduct.
Release
OpenZFS is released under a CDDL license.
For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197
Supported Kernels and Distributions
Linux
Given the wide variety of Linux environments, we prioritize development and testing on stable, supported kernels and distributions.
Kernel (kernel.org)
All longterm kernels from kernel.org are supported. stable kernels are usually supported in the next OpenZFS release.
Supported longterm kernels: 6.18, 6.12, 6.6, 6.1, 5.15, 5.10.
Red Hat Enterprise Linux (RHEL)
All RHEL (and compatible systems: AlmaLinux OS, Rocky Linux, etc) on the full or maintenance support tracks are supported.
Supported RHEL releases: 8.10, 9.7, 10.1.
Ubuntu
All Ubuntu LTS releases are supported.
Supported Ubuntu releases: 24.04 “Noble”, 22.04 “Jammy”.
Debian
All Debian stable and LTS releases are supported.
Supported Debian releases: 13 “Trixie”, 12 “Bookworm”, 11 “Bullseye”.
Other Distributions
Generally, if a distribution is following an LTS kernel, it should work well with OpenZFS.
FreeBSD
All FreeBSD releases receiving security support are supported by OpenZFS.
Supported FreeBSD releases: 15.0, 14.3, 13.5.