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

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: 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: 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

ovl: lookup connected ancestor of dir in inode cache

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

Decoding a dir file handle requires walking backward up to layer root and
for lower dir also checking the index to see if any of the parents have
been copied up.

Lookup overlay ancestor dentry in inode/dentry cache by decoded real
parents to shortcut looking up all the way back to layer root.

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

ovl: decode pure lower dir file handles

2018-01-24T10:26:04+00:00

Similar to decoding a pure upper dir file handle, decoding a pure lower
dir file handle is implemented by looking an overlay dentry of the same
path as the pure lower path and verifying that the overlay dentry's
real lower matches the decoded real lower file handle.

Unlike the case of upper dir file handle, the lookup of overlay path by
lower real path can fail or find a mismatched overlay dentry if any of
the lower parents have been copied up and renamed. To address this case
we will need to check if any of the lower parents are indexed.

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

ovl: decode indexed dir file handles

2018-01-24T10:26:03+00:00

Decoding an indexed dir file handle is done by looking up the file handle
in index dir by name and then decoding the upper dir from the index origin
file handle. The decoded upper path is used to lookup an overlay dentry of
the same path.

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

ovl: decode lower file handles of unlinked but open files

2018-01-24T10:26:03+00:00

Lookup overlay inode in cache by origin inode, so we can decode a file
handle of an open file even if the index has a whiteout index entry to
mark this overlay inode was unlinked.

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

ovl: decode indexed non-dir file handles

2018-01-24T10:26:03+00:00

Decoding an indexed non-dir file handle is similar to decoding a lower
non-dir file handle, but additionally, we lookup the file handle in index
dir by name to find the real upper inode.

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