WSL2-Linux-Kernel/fs/nfs
Eric W. Biederman 0481f001d9 fs: Teach path_connected to handle nfs filesystems with multiple roots.
commit 95dd77580c upstream.

On nfsv2 and nfsv3 the nfs server can export subsets of the same
filesystem and report the same filesystem identifier, so that the nfs
client can know they are the same filesystem.  The subsets can be from
disjoint directory trees.  The nfsv2 and nfsv3 filesystems provides no
way to find the common root of all directory trees exported form the
server with the same filesystem identifier.

The practical result is that in struct super s_root for nfs s_root is
not necessarily the root of the filesystem.  The nfs mount code sets
s_root to the root of the first subset of the nfs filesystem that the
kernel mounts.

This effects the dcache invalidation code in generic_shutdown_super
currently called shrunk_dcache_for_umount and that code for years
has gone through an additional list of dentries that might be dentry
trees that need to be freed to accomodate nfs.

When I wrote path_connected I did not realize nfs was so special, and
it's hueristic for avoiding calling is_subdir can fail.

The practical case where this fails is when there is a move of a
directory from the subtree exposed by one nfs mount to the subtree
exposed by another nfs mount.  This move can happen either locally or
remotely.  With the remote case requiring that the move directory be cached
before the move and that after the move someone walks the path
to where the move directory now exists and in so doing causes the
already cached directory to be moved in the dcache through the magic
of d_splice_alias.

If someone whose working directory is in the move directory or a
subdirectory and now starts calling .. from the initial mount of nfs
(where s_root == mnt_root), then path_connected as a heuristic will
not bother with the is_subdir check.  As s_root really is not the root
of the nfs filesystem this heuristic is wrong, and the path may
actually not be connected and path_connected can fail.

The is_subdir function might be cheap enough that we can call it
unconditionally.  Verifying that will take some benchmarking and
the result may not be the same on all kernels this fix needs
to be backported to.  So I am avoiding that for now.

Filesystems with snapshots such as nilfs and btrfs do something
similar.  But as the directory tree of the snapshots are disjoint
from one another and from the main directory tree rename won't move
things between them and this problem will not occur.

Cc: stable@vger.kernel.org
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Fixes: 397d425dc2 ("vfs: Test for and handle paths that are unreachable from their mnt_root")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-03-21 12:06:43 +01:00
..
blocklayout License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
filelayout nfs41: do not return ENOMEM on LAYOUTUNAVAILABLE 2018-02-16 20:22:58 +01:00
flexfilelayout License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig pnfs/blocklayout: require 64-bit sector_t 2017-08-11 14:10:13 -04:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cache_lib.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cache_lib.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
callback.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
callback.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
callback_proc.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
callback_xdr.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
client.c NFS: Fix uninitialized rpc_wait_queue 2017-10-01 18:51:30 -04:00
delegation.c NFS: Use an atomic_long_t to count the number of requests 2017-08-15 11:54:47 -04:00
delegation.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dir.c NFS: Fix a typo in nfs_rename() 2017-12-14 09:53:08 +01:00
direct.c NFS: Fix an incorrect type in struct nfs_direct_req 2018-03-15 10:54:27 +01:00
dns_resolve.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dns_resolve.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
export.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
file.c NFS: Revert "NFS: Move the flock open mode check into nfs_flock()" 2017-11-30 08:40:46 +00:00
fscache-index.c fscache: remove unused ->now_uncached callback 2017-09-06 17:27:26 -07:00
fscache.c nfs: define nfs_inc_fscache_stats and using it as possible 2014-11-24 20:08:47 -05:00
fscache.h
getroot.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
inode.c NFS: Use an atomic_long_t to count the number of commits 2017-08-15 11:54:48 -04:00
internal.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
io.c NFS: Fix a race between mmap() and O_DIRECT 2018-02-16 20:22:59 +01:00
iostat.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mount_clnt.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
namespace.c NFS: Use ERR_CAST() to avoid cross-structure cast 2017-05-28 10:11:47 -07:00
netns.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs2super.c
nfs2xdr.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs3_fs.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs3acl.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs3client.c NFS: Remove unused authflavour parameter from nfs_get_client() 2016-12-01 17:46:32 -05:00
nfs3proc.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs3super.c nfsv3: introduce nfs3_set_ds_client 2015-02-03 11:06:34 -08:00
nfs3xdr.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs4_fs.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs4client.c NFSv4: Fix double frees in nfs4_test_session_trunk() 2017-08-02 09:45:55 -04:00
nfs4file.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs4getroot.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs4idmap.c NFS: reject request for id_legacy key without auxdata 2018-02-16 20:22:58 +01:00
nfs4idmap.h NFS: Move nfs_idmap.h into fs/nfs/ 2015-04-23 15:16:14 -04:00
nfs4namespace.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs4proc.c nfs: Fix ugly referral attributes 2017-11-30 08:40:46 +00:00
nfs4renewd.c NFSv4: Set the connection timeout to match the lease period 2017-02-09 14:15:16 -05:00
nfs4session.c NFSv4.1: Fix regression in callback retry handling 2016-12-01 17:21:38 -05:00
nfs4session.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs4state.c NFS client updates for Linux 4.13 2017-07-13 14:35:37 -07:00
nfs4super.c NFS: Move nfs_idmap.h into fs/nfs/ 2015-04-23 15:16:14 -04:00
nfs4sysctl.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs4trace.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs4trace.h NFS: Avoid RCU usage in tracepoints 2017-11-30 08:40:46 +00:00
nfs4xdr.c NFS: Fix nfsstat breakage due to LOOKUPP 2018-02-16 20:22:58 +01:00
nfs42.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs42proc.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfs42xdr.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfsroot.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfstrace.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nfstrace.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pagelist.c NFS: various changes relating to reporting IO errors. 2017-09-11 22:28:56 -04:00
pnfs.c pNFS: Prevent the layout header refcount going to zero in pnfs_roc() 2018-03-15 10:54:27 +01:00
pnfs.h NFSv4/pnfs: Replace pnfs_put_lseg_locked() with pnfs_put_lseg() 2017-08-15 11:54:48 -04:00
pnfs_dev.c NFSv4.1: Don't cache deviceids that have no notifications 2015-03-27 12:32:24 -04:00
pnfs_nfs.c NFS: Remove pnfs_generic_transfer_commit_list() 2017-09-09 12:51:40 -04:00
proc.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
read.c NFS: Add static NFS I/O tracepoints 2017-09-11 22:20:38 -04:00
super.c fs: Teach path_connected to handle nfs filesystems with multiple roots. 2018-03-21 12:06:43 +01:00
symlink.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
sysctl.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
unlink.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
write.c NFS: Fix unstable write completion 2018-03-15 10:54:27 +01:00