linux.git/fs/overlayfs, branch v4.16

ovl: update Kconfig texts

2018-03-07T10:47:15+00:00

Add some hints about overlayfs kernel config options.

Enabling NFS export by default is especially recommended against, as it
incurs a performance penalty even if the filesystem is not actually
exported.

Signed-off-by: Miklos Szeredi

ovl: redirect_dir=nofollow should not follow redirect for opaque lower

2018-02-26T15:55:51+00:00

redirect_dir=nofollow should not follow a redirect. But in a specific
configuration it can still follow it.  For example try this.

$ mkdir -p lower0 lower1/foo upper work merged
$ touch lower1/foo/lower-file.txt
$ setfattr -n "trusted.overlay.opaque" -v "y" lower1/foo
$ mount -t overlay -o lowerdir=lower1:lower0,workdir=work,upperdir=upper,redirect_dir=on none merged
$ cd merged
$ mv foo foo-renamed
$ umount merged

# mount again. This time with redirect_dir=nofollow
$ mount -t overlay -o lowerdir=lower1:lower0,workdir=work,upperdir=upper,redirect_dir=nofollow none merged
$ ls merged/foo-renamed/
# This lists lower-file.txt, while it should not have.

Basically, we are doing redirect check after we check for d.stop. And
if this is not last lower, and we find an opaque lower, d.stop will be
set.

ovl_lookup_single()
        if (!d->last && ovl_is_opaquedir(this)) {
                d->stop = d->opaque = true;
                goto out;
        }

To fix this, first check redirect is allowed. And after that check if
d.stop has been set or not.

Signed-off-by: Vivek Goyal 
Fixes: 438c84c2f0c7 ("ovl: don't follow redirects if redirect_dir=off")
Cc:  #v4.15
Signed-off-by: Miklos Szeredi

ovl: fix ptr_ret.cocci warnings

2018-02-26T11:45:20+00:00

fs/overlayfs/export.c:459:10-16: WARNING: PTR_ERR_OR_ZERO can be used

 Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci

Fixes: 4b91c30a5a19 ("ovl: lookup connected ancestor of dir in inode cache")
CC: Amir Goldstein 
Signed-off-by: Fengguang Wu 
Signed-off-by: Miklos Szeredi

ovl: check ERR_PTR() return value from ovl_lookup_real()

2018-02-16T14:53:20+00:00

Reported-by: Dan Carpenter 
Fixes: 061701540349 ("ovl: lookup indexed ancestor of lower dir")
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: check lower ancestry on encode of lower dir file handle

2018-02-16T14:53:20+00:00

This change relaxes copy up on encode of merge dir with lower layer > 1
and handles the case of encoding a merge dir with lower layer 1, where an
ancestor is a non-indexed merge dir. In that case, decode of the lower
file handle will not have been possible if the non-indexed ancestor is
redirected before or after encode.

Before encoding a non-upper directory file handle from real layer N, we
need to check if it will be possible to reconnect an overlay dentry from
the real lower decoded dentry. This is done by following the overlay
ancestry up to a "layer N connected" ancestor and verifying that all
parents along the way are "layer N connectable". If an ancestor that is
NOT "layer N connectable" is found, we need to copy up an ancestor, which
is "layer N connectable", thus making that ancestor "layer N connected".
For example:

 layer 1: /a
 layer 2: /a/b/c

The overlay dentry /a is NOT "layer 2 connectable", because if dir /a is
copied up and renamed, upper dir /a will be indexed by lower dir /a from
layer 1. The dir /a from layer 2 will never be indexed, so the algorithm
in ovl_lookup_real_ancestor() (*) will not be able to lookup a connected
overlay dentry from the connected lower dentry /a/b/c.

To avoid this problem on decode time, we need to copy up an ancestor of
/a/b/c, which is "layer 2 connectable", on encode time. That ancestor is
/a/b. After copy up (and index) of /a/b, it will become "layer 2 connected"
and when the time comes to decode the file handle from lower dentry /a/b/c,
ovl_lookup_real_ancestor() will find the indexed ancestor /a/b and decoding
a connected overlay dentry will be accomplished.

(*) the algorithm in ovl_lookup_real_ancestor() can be improved to lookup
an entry /a in the lower layers above layer N and find the indexed dir /a
from layer 1. If that improvement is made, then the check for "layer N
connected" will need to verify there are no redirects in lower layers above
layer N. In the example above, /a will be "layer 2 connectable". However,
if layer 2 dir /a is a target of a layer 1 redirect, then /a will NOT be
"layer 2 connectable":

 layer 1: /A (redirect = /a)
 layer 2: /a/b/c

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: hash non-dir by lower inode for fsnotify

2018-02-16T14:53:20+00:00

Commit 31747eda41ef ("ovl: hash directory inodes for fsnotify")
fixed an issue of inotify watch on directory that stops getting
events after dropping dentry caches.

A similar issue exists for non-dir non-upper files, for example:

$ mkdir -p lower upper work merged
$ touch lower/foo
$ mount -t overlay -o
lowerdir=lower,workdir=work,upperdir=upper none merged
$ inotifywait merged/foo &
$ echo 2 > /proc/sys/vm/drop_caches
$ cat merged/foo

inotifywait doesn't get the OPEN event, because ovl_lookup() called
from 'cat' allocates a new overlay inode and does not reuse the
watched inode.

Fix this by hashing non-dir overlay inodes by lower real inode in
the following cases that were not hashed before this change:
 - A non-upper overlay mount
 - A lower non-hardlink when index=off

A helper ovl_hash_bylower() was added to put all the logic and
documentation about which real inode an overlay inode is hashed by
into one place.

The issue dates back to initial version of overlayfs, but this
patch depends on ovl_inode code that was introduced in kernel v4.13.

Cc:  #v4.13
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: check ERR_PTR() return value from ovl_encode_fh()

2018-02-05T08:50:29+00:00

Another fix for an issue reported by 0-day robot.

Reported-by: Dan Carpenter 
Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles")
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: fix regression in fsnotify of overlay merge dir

2018-02-05T08:50:29+00:00

A re-factoring patch in NFS export series has passed the wrong argument
to ovl_get_inode() causing a regression in the very recent fix to
fsnotify of overlay merge dir.

The regression has caused merge directory inodes to be hashed by upper
instead of lower real inode, when NFS export and directory indexing is
disabled. That caused an inotify watch to become obsolete after directory
copy up and drop caches.

LTP test inotify07 was improved to catch this regression.
The regression also caused multiple redirect dirs to same origin not to
be detected on lookup with NFS export disabled. An xfstest was added to
cover this case.

Fixes: 0aceb53e73be ("ovl: do not pass overlay dentry to ovl_get_inode()")
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: wire up NFS export operations

2018-01-24T10:26:06+00:00

Now that NFS export operations are implemented, enable overlayfs NFS
export support if the "nfs_export" feature is enabled.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: lookup indexed ancestor of lower dir

2018-01-24T10:26:05+00:00

ovl_lookup_real() in lower layer walks back lower parents to find the
topmost indexed parent. If an indexed ancestor is found before reaching
lower layer root, ovl_lookup_real() is called recursively with upper
layer to walk back from indexed upper to the topmost connected/hashed
upper parent (or up to root).

ovl_lookup_real() in upper layer then walks forward to connect the topmost
upper overlay dir dentry and ovl_lookup_real() in lower layer continues to
walk forward to connect the decoded lower overlay dir dentry.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi