linux-stable.git/fs/overlayfs, branch linux-5.0.y

ovl: relax WARN_ON() for overlapping layers use case

2019-05-31T13:44:47+00:00

commit acf3062a7e1ccf67c6f7e7c28671a6708fde63b0 upstream.

This nasty little syzbot repro:
https://syzkaller.appspot.com/x/repro.syz?x=12c7a94f400000

Creates overlay mounts where the same directory is both in upper and lower
layers. Simplified example:

  mkdir foo work
  mount -t overlay none foo -o"lowerdir=.,upperdir=foo,workdir=work"

The repro runs several threads in parallel that attempt to chdir into foo
and attempt to symlink/rename/exec/mkdir the file bar.

The repro hits a WARN_ON() I placed in ovl_instantiate(), which suggests
that an overlay inode already exists in cache and is hashed by the pointer
of the real upper dentry that ovl_create_real() has just created. At the
point of the WARN_ON(), for overlay dir inode lock is held and upper dir
inode lock, so at first, I did not see how this was possible.

On a closer look, I see that after ovl_create_real(), because of the
overlapping upper and lower layers, a lookup by another thread can find the
file foo/bar that was just created in upper layer, at overlay path
foo/foo/bar and hash the an overlay inode with the new real dentry as lower
dentry. This is possible because the overlay directory foo/foo is not
locked and the upper dentry foo/bar is in dcache, so ovl_lookup() can find
it without taking upper dir inode shared lock.

Overlapping layers is considered a wrong setup which would result in
unexpected behavior, but it shouldn't crash the kernel and it shouldn't
trigger WARN_ON() either, so relax this WARN_ON() and leave a pr_warn()
instead to cover all cases of failure to get an overlay inode.

The error returned from failure to insert new inode to cache with
inode_insert5() was changed to -EEXIST, to distinguish from the error
-ENOMEM returned on failure to get/allocate inode with iget5_locked().

Reported-by: syzbot+9c69c282adc4edd2b540@syzkaller.appspotmail.com
Fixes: 01b39dcc9568 ("ovl: use inode_insert5() to hash a newly...")
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: fix missing upper fs freeze protection on copy up for ioctl

2019-05-25T16:22:10+00:00

commit 3428030da004a1128cbdcf93dc03e16f184d845b upstream.

Generalize the helper ovl_open_maybe_copy_up() and use it to copy up file
with data before FS_IOC_SETFLAGS ioctl.

The FS_IOC_SETFLAGS ioctl is a bit of an odd ball in vfs, which probably
caused the confusion.  File may be open O_RDONLY, but ioctl modifies the
file.  VFS does not call mnt_want_write_file() nor lock inode mutex, but
fs-specific code for FS_IOC_SETFLAGS does.  So ovl_ioctl() calls
mnt_want_write_file() for the overlay file, and fs-specific code calls
mnt_want_write_file() for upper fs file, but there was no call for
ovl_want_write() for copy up duration which prevents overlayfs from copying
up on a frozen upper fs.

Fixes: dab5ca8fd9dd ("ovl: add lsattr/chattr support")
Cc:  # v4.19
Signed-off-by: Amir Goldstein 
Acked-by: Vivek Goyal 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: Do not lose security.capability xattr over metadata file copy-up

2019-03-23T19:11:21+00:00

commit 993a0b2aec52754f0897b1dab4c453be8217cae5 upstream.

If a file has been copied up metadata only, and later data is copied up,
upper loses any security.capability xattr it has (underlying filesystem
clears it as upon file write).

From a user's point of view, this is just a file copy-up and that should
not result in losing security.capability xattr.  Hence, before data copy
up, save security.capability xattr (if any) and restore it on upper after
data copy up is complete.

Signed-off-by: Vivek Goyal 
Reviewed-by: Amir Goldstein 
Fixes: 0c2888749363 ("ovl: A new xattr OVL_XATTR_METACOPY for file on upper")
Cc:  # v4.19+
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: During copy up, first copy up data and then xattrs

2019-03-23T19:11:21+00:00

commit 5f32879ea35523b9842bdbdc0065e13635caada2 upstream.

If a file with capability set (and hence security.capability xattr) is
written kernel clears security.capability xattr. For overlay, during file
copy up if xattrs are copied up first and then data is, copied up. This
means data copy up will result in clearing of security.capability xattr
file on lower has. And this can result into surprises. If a lower file has
CAP_SETUID, then it should not be cleared over copy up (if nothing was
actually written to file).

This also creates problems with chown logic where it first copies up file
and then tries to clear setuid bit. But by that time security.capability
xattr is already gone (due to data copy up), and caller gets -ENODATA.
This has been reported by Giuseppe here.

https://github.com/containers/libpod/issues/2015#issuecomment-447824842

Fix this by copying up data first and then metadta. This is a regression
which has been introduced by my commit as part of metadata only copy up
patches.

TODO: There will be some corner cases where a file is copied up metadata
only and later data copy up happens and that will clear security.capability
xattr. Something needs to be done about that too.

Fixes: bd64e57586d3 ("ovl: During copy up, first copy up metadata and then data")
Cc:  # v4.19+
Reported-by: Giuseppe Scrivano 
Signed-off-by: Vivek Goyal 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

Revert "ovl: relax permission checking on underlying layers"

2018-12-04T10:31:30+00:00

This reverts commit 007ea44892e6fa963a0876a979e34890325c64eb.

The commit broke some selinux-testsuite cases, and it looks like there's no
straightforward fix keeping the direction of this patch, so revert for now.

The original patch was trying to fix the consistency of permission checks, and
not an observed bug.  So reverting should be safe.

Signed-off-by: Miklos Szeredi

ovl: fix decode of dir file handle with multi lower layers

2018-11-21T09:44:48+00:00

When decoding a lower file handle, we first call ovl_check_origin_fh()
with connected=false to get any real lower dentry for overlay inode
cache lookup.

If the real dentry is a disconnected dir dentry, ovl_check_origin_fh()
is called again with connected=true to get a connected real dentry
and find the lower layer the real dentry belongs to.

If the first call returned a connected real dentry, we use it to
lookup an overlay connected dentry, but the first ovl_check_origin_fh()
call with connected=false did not check that the found dentry is under
the root of the layer (see ovl_acceptable()), it only checked that
the found dentry super block matches the uuid of the lower file handle.

In case there are multiple lower layers on the same fs and the found
dentry is not from the top most lower layer, using the layer index
returned from the first ovl_check_origin_fh() is wrong and we end
up failing to decode the file handle.

Fix this by always calling ovl_check_origin_fh() with connected=true
if we got a directory dentry in the first call.

Fixes: 8b58924ad55c ("ovl: lookup in inode cache first when decoding...")
Cc:  # v4.17
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: fix missing override creds in link of a metacopy upper

2018-11-19T15:21:29+00:00

Theodore Ts'o reported a v4.19 regression with docker-dropbox:
https://marc.info/?l=linux-fsdevel&m=154070089431116&w=2

"I was rebuilding my dropbox Docker container, and it failed in 4.19
 with the following error:
 ...
 dpkg: error: error creating new backup file \
              '/var/lib/dpkg/status-old': Invalid cross-device link"

The problem did not reproduce with metacopy feature disabled.
The error was caused by insufficient credentials to set
"trusted.overlay.redirect" xattr on link of a metacopy file.

Reproducer:

 echo Y > /sys/module/overlay/parameters/redirect_dir
 echo Y > /sys/module/overlay/parameters/metacopy
 cd /tmp
 mkdir l u w m
 chmod 777 l u
 touch l/foo
 ln l/foo l/link
 chmod 666 l/foo
 mount -t overlay none -olowerdir=l,upperdir=u,workdir=w m
 su fsgqa
 ln m/foo m/bar
 [   21.455823] overlayfs: failed to set redirect (-1)
 ln: failed to create hard link 'm/bar' => 'm/foo':\
     Invalid cross-device link

Reported-by: Theodore Y. Ts'o 
Reported-by: Maciej Zięba 
Fixes: 4120fe64dce4 ("ovl: Set redirect on upper inode when it is linked")
Cc:  # v4.19
Signed-off-by: Amir Goldstein 
Acked-by: Vivek Goyal 
Signed-off-by: Miklos Szeredi

Merge tag 'xfs-4.20-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

2018-11-02T16:33:08+00:00

Pull vfs dedup fixes from Dave Chinner:
 "This reworks the vfs data cloning infrastructure.

  We discovered many issues with these interfaces late in the 4.19 cycle
  - the worst of them (data corruption, setuid stripping) were fixed for
  XFS in 4.19-rc8, but a larger rework of the infrastructure fixing all
  the problems was needed. That rework is the contents of this pull
  request.

  Rework the vfs_clone_file_range and vfs_dedupe_file_range
  infrastructure to use a common .remap_file_range method and supply
  generic bounds and sanity checking functions that are shared with the
  data write path. The current VFS infrastructure has problems with
  rlimit, LFS file sizes, file time stamps, maximum filesystem file
  sizes, stripping setuid bits, etc and so they are addressed in these
  commits.

  We also introduce the ability for the ->remap_file_range methods to
  return short clones so that clones for vfs_copy_file_range() don't get
  rejected if the entire range can't be cloned. It also allows
  filesystems to sliently skip deduplication of partial EOF blocks if
  they are not capable of doing so without requiring errors to be thrown
  to userspace.

  Existing filesystems are converted to user the new remap_file_range
  method, and both XFS and ocfs2 are modified to make use of the new
  generic checking infrastructure"

* tag 'xfs-4.20-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: (28 commits)
  xfs: remove [cm]time update from reflink calls
  xfs: remove xfs_reflink_remap_range
  xfs: remove redundant remap partial EOF block checks
  xfs: support returning partial reflink results
  xfs: clean up xfs_reflink_remap_blocks call site
  xfs: fix pagecache truncation prior to reflink
  ocfs2: remove ocfs2_reflink_remap_range
  ocfs2: support partial clone range and dedupe range
  ocfs2: fix pagecache truncation prior to reflink
  ocfs2: truncate page cache for clone destination file before remapping
  vfs: clean up generic_remap_file_range_prep return value
  vfs: hide file range comparison function
  vfs: enable remap callers that can handle short operations
  vfs: plumb remap flags through the vfs dedupe functions
  vfs: plumb remap flags through the vfs clone functions
  vfs: make remap_file_range functions take and return bytes completed
  vfs: remap helper should update destination inode metadata
  vfs: pass remap flags to generic_remap_checks
  vfs: pass remap flags to generic_remap_file_range_prep
  vfs: combine the clone and dedupe into a single remap_file_range
  ...

ovl: automatically enable redirect_dir on metacopy=on

2018-11-01T20:31:39+00:00

Current behavior is to automatically disable metacopy if redirect_dir is
not enabled and proceed with the mount.

If "metacopy=on" mount option was given, then this behavior can confuse the
user: no mount failure, yet metacopy is disabled.

This patch makes metacopy=on imply redirect_dir=on.

The converse is also true: turning off full redirect with redirect_dir=
{off|follow|nofollow} will disable metacopy.

If both metacopy=on and redirect_dir={off|follow|nofollow} is specified,
then mount will fail, since there's no way to correctly resolve the
conflict.

Reported-by: Daniel Walsh 
Fixes: d5791044d2e5 ("ovl: Provide a mount option metacopy=on/off...")
Cc:  # v4.19
Signed-off-by: Miklos Szeredi

ovl: check whiteout in ovl_create_over_whiteout()

2018-10-31T11:15:23+00:00

Kaixuxia repors that it's possible to crash overlayfs by removing the
whiteout on the upper layer before creating a directory over it.  This is a
reproducer:

 mkdir lower upper work merge
 touch lower/file
 mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge
 rm merge/file
 ls -al merge/file
 rm upper/file
 ls -al merge/
 mkdir merge/file

Before commencing with a vfs_rename(..., RENAME_EXCHANGE) verify that the
lookup of "upper" is positive and is a whiteout, and return ESTALE
otherwise.

Reported by: kaixuxia 
Signed-off-by: Miklos Szeredi 
Fixes: e9be9d5e76e3 ("overlay filesystem")
Cc:  # v3.18