linux-stable.git/fs/overlayfs, branch linux-4.9.y

ovl: fix missing negative dentry check in ovl_rename()

2021-10-17T08:05:38+00:00

commit a295aef603e109a47af355477326bd41151765b6 upstream.

The following reproducer

  mkdir lower upper work merge
  touch lower/old
  touch lower/new
  mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge
  rm merge/new
  mv merge/old merge/new & unlink upper/new

may result in this race:

PROCESS A:
  rename("merge/old", "merge/new");
  overwrite=true,ovl_lower_positive(old)=true,
  ovl_dentry_is_whiteout(new)=true -> flags |= RENAME_EXCHANGE

PROCESS B:
  unlink("upper/new");

PROCESS A:
  lookup newdentry in new_upperdir
  call vfs_rename() with negative newdentry and RENAME_EXCHANGE

Fix by adding the missing check for negative newdentry.

Signed-off-by: Zheng Liang 
Fixes: e9be9d5e76e3 ("overlay filesystem")
Cc:  # v3.18
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: skip getxattr of security labels

2021-02-23T12:59:15+00:00

[ Upstream commit 03fedf93593c82538b18476d8c4f0e8f8435ea70 ]

When inode has no listxattr op of its own (e.g. squashfs) vfs_listxattr
calls the LSM inode_listsecurity hooks to list the xattrs that LSMs will
intercept in inode_getxattr hooks.

When selinux LSM is installed but not initialized, it will list the
security.selinux xattr in inode_listsecurity, but will not intercept it
in inode_getxattr.  This results in -ENODATA for a getxattr call for an
xattr returned by listxattr.

This situation was manifested as overlayfs failure to copy up lower
files from squashfs when selinux is built-in but not initialized,
because ovl_copy_xattr() iterates the lower inode xattrs by
vfs_listxattr() and vfs_getxattr().

ovl_copy_xattr() skips copy up of security labels that are indentified by
inode_copy_up_xattr LSM hooks, but it does that after vfs_getxattr().
Since we are not going to copy them, skip vfs_getxattr() of the security
labels.

Reported-by: Michael Labriola 
Tested-by: Michael Labriola 
Link: https://lore.kernel.org/linux-unionfs/2nv9d47zt7.fsf@aldarion.sourceruckus.org/
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin

ovl: initialize error in ovl_copy_xattr

2020-06-20T08:24:11+00:00

commit 520da69d265a91c6536c63851cbb8a53946974f0 upstream.

In ovl_copy_xattr, if all the xattrs to be copied are overlayfs private
xattrs, the copy loop will terminate without assigning anything to the
error variable, thus returning an uninitialized value.

If ovl_copy_xattr is called from ovl_clear_empty, this uninitialized error
value is put into a pointer by ERR_PTR(), causing potential invalid memory
accesses down the line.

This commit initialize error with 0. This is the correct value because when
there's no xattr to copy, because all xattrs are private, ovl_copy_xattr
should succeed.

This bug is discovered with the help of INIT_STACK_ALL and clang.

Signed-off-by: Yuxuan Shui 
Link: https://bugs.chromium.org/p/chromium/issues/detail?id=1050405
Fixes: 0956254a2d5b ("ovl: don't copy up opaqueness")
Cc: stable@vger.kernel.org # v4.8
Signed-off-by: Alexander Potapenko 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: filter of trusted xattr results in audit

2019-10-05T10:30:34+00:00

commit 5c2e9f346b815841f9bed6029ebcb06415caf640 upstream.

When filtering xattr list for reading, presence of trusted xattr
results in a security audit log.  However, if there is other content
no errno will be set, and if there isn't, the errno will be -ENODATA
and not -EPERM as is usually associated with a lack of capability.
The check does not block the request to list the xattrs present.

Switch to ns_capable_noaudit to reflect a more appropriate check.

Signed-off-by: Mark Salyzyn 
Cc: linux-security-module@vger.kernel.org
Cc: kernel-team@android.com
Cc: stable@vger.kernel.org # v3.18+
Fixes: a082c6f680da ("ovl: filter trusted xattr for non-admin")
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: filter trusted xattr for non-admin

2018-04-13T17:48:12+00:00

[ Upstream commit a082c6f680da298cf075886ff032f32ccb7c5e1a ]

Filesystems filter out extended attributes in the "trusted." domain for
unprivlieged callers.

Overlay calls underlying filesystem's method with elevated privs, so need
to do the filtering in overlayfs too.

Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

ovl: persistent inode numbers for upper hardlinks

2018-04-13T17:47:50+00:00

[ Upstream commit 5b6c9053fb38a66fd5c6177fcf5022b24767811a ]

An upper type non directory dentry that is a copy up target
should have a reference to its lower copy up origin.

There are three ways for an upper type dentry to be instantiated:
1. A lower type dentry that is being copied up
2. An entry that is found in upper dir by ovl_lookup()
3. A negative dentry is hardlinked to an upper type dentry

In the first case, the lower reference is set before copy up.
In the second case, the lower reference is found by ovl_lookup().
In the last case of hardlinked upper dentry, it is not easy to
update the lower reference of the negative dentry.  Instead,
drop the newly hardlinked negative dentry from dcache and let
the next access call ovl_lookup() to find its lower reference.

This makes sure that the inode number reported by stat(2) after
the hardlink is created is the same inode number that will be
reported by stat(2) after mount cycle, which is the inode number
of the lower copy up origin of the hardlink source.

NOTE that this does not fix breaking of lower hardlinks on copy
up, but only fixes the case of lower nlink == 1, whose upper copy
up inode is hardlinked in upper dir.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

ovl: fix failure to fsync lower dir

2018-02-17T12:21:20+00:00

commit d796e77f1dd541fe34481af2eee6454688d13982 upstream.

As a writable mount, it is not expected for overlayfs to return
EINVAL/EROFS for fsync, even if dir/file is not changed.

This commit fixes the case of fsync of directory, which is easier to
address, because overlayfs already implements fsync file operation for
directories.

The problem reported by Raphael is that new PostgreSQL 10.0 with a
database in overlayfs where lower layer in squashfs fails to start.
The failure is due to fsync error, when PostgreSQL does fsync on all
existing db directories on startup and a specific directory exists
lower layer with no changes.

Reported-by: Raphael Hertzog 
Signed-off-by: Amir Goldstein 
Tested-by: Raphaël Hertzog 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: fix random return value on mount

2017-07-27T22:08:07+00:00

commit 8fc646b44385ff0a9853f6590497e43049eeb311 upstream.

On failure to prepare_creds(), mount fails with a random
return value, as err was last set to an integer cast of
a valid lower mnt pointer or set to 0 if inodes index feature
is enabled.

Reported-by: Dan Carpenter 
Fixes: 3fe6e52f0626 ("ovl: override creds with the ones from ...")
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: drop CAP_SYS_RESOURCE from saved mounter's credentials

2017-07-27T22:08:03+00:00

commit 51f8f3c4e22535933ef9aecc00e9a6069e051b57 upstream.

If overlay was mounted by root then quota set for upper layer does not work
because overlay now always use mounter's credentials for operations.
Also overlay might deplete reserved space and inodes in ext4.

This patch drops capability SYS_RESOURCE from saved credentials.
This affects creation new files, whiteouts, and copy-up operations.

Signed-off-by: Konstantin Khlebnikov 
Fixes: 1175b6b8d963 ("ovl: do operations on underlying file system in mounter's context")
Cc: Vivek Goyal 
Signed-off-by: Miklos Szeredi 
Cc: Amir Goldstein 
Signed-off-by: Greg Kroah-Hartman

ovl: fix d_real() for stacked fs

2016-11-29T09:20:24+00:00

Handling of recursion in d_real() is completely broken.  Recursion is only
done in the 'inode != NULL' case.  But when opening the file we have
'inode == NULL' hence d_real() will return an overlay dentry.  This won't
work since overlayfs doesn't define its own file operations, so all file
ops will fail.

Fix by doing the recursion first and the check against the inode second.

Bash script to reproduce the issue written by Quentin:

 - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - -
tmpdir=$(mktemp -d)
pushd ${tmpdir}

mkdir -p {upper,lower,work}
echo -n 'rocks' > lower/ksplice
mount -t overlay level_zero upper -o lowerdir=lower,upperdir=upper,workdir=work
cat upper/ksplice

tmpdir2=$(mktemp -d)
pushd ${tmpdir2}

mkdir -p {upper,work}
mount -t overlay level_one upper -o lowerdir=${tmpdir}/upper,upperdir=upper,workdir=work
ls -l upper/ksplice
cat upper/ksplice
 - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - 

Reported-by: Quentin Casasnovas 
Signed-off-by: Miklos Szeredi 
Fixes: 2d902671ce1c ("vfs: merge .d_select_inode() into .d_real()")
Cc:  # v4.8+