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* [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off
@ 2019-07-31 16:57 Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 1/5] overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh Mark Salyzyn via Linux-f2fs-devel
                   ` (5 more replies)
  0 siblings, 6 replies; 7+ messages in thread
From: Mark Salyzyn via Linux-f2fs-devel @ 2019-07-31 16:57 UTC (permalink / raw)
  To: linux-kernel
  Cc: Latchesar Ionkov, Dave Kleikamp, jfs-discussion, Randy Dunlap,
	linux-doc, Martin Brandenburg, samba-technical,
	Dominique Martinet, Amir Goldstein, David Howells, Chris Mason,
	David S . Miller, Andreas Dilger, ocfs2-devel, netdev,
	Tyler Hicks, linux-afs, Mike Marshall, linux-xfs,
	Andreas Gruenbacher, Sage Weil, Jonathan Corbet,
	Richard Weinberger, Mark Fasheh, devel, Hugh Dickins,
	linux-security-module, cluster-devel, Vyacheslav Dubeyko,
	v9fs-developer, Ilya Dryomov, linux-ext4, Stephen Smalley,
	linux-mm, Vivek Goyal, linux-cifs, Eric Van Hensbergen, ecryptfs,
	Josef Bacik, Darrick J . Wong, reiserfs-devel, Tejun Heo,
	Greg Kroah-Hartman, Joel Becker, linux-mtd, David Sterba,
	Jaegeuk Kim, ceph-devel, Trond Myklebust, linux-nfs,
	linux-f2fs-devel, Theodore Ts\'o, linux-fsdevel, Joseph Qi,
	Mathieu Malaterre, kernel-team, Miklos Szeredi, Jeff Layton,
	linux-unionfs, stable, Mark Salyzyn, Steve French,
	Ernesto A . Fernández, Eric W . Biederman, Jan Kara,
	Bob Peterson, Phillip Lougher, Andrew Morton, David Woodhouse,
	Anna Schumaker, linux-btrfs, Alexander Viro

Patch series:

overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh
Add flags option to get xattr method paired to __vfs_getxattr
overlayfs: handle XATTR_NOSECURITY flag for get xattr method
overlayfs: internal getxattr operations without sepolicy checking
overlayfs: override_creds=off option bypass creator_cred

The first four patches address fundamental security issues that should
be solved regardless of the override_creds=off feature.
on them).

The fifth adds the feature depends on these other fixes.

By default, all access to the upper, lower and work directories is the
recorded mounter's MAC and DAC credentials.  The incoming accesses are
checked against the caller's credentials.

If the principles of least privilege are applied for sepolicy, the
mounter's credentials might not overlap the credentials of the caller's
when accessing the overlayfs filesystem.  For example, a file that a
lower DAC privileged caller can execute, is MAC denied to the
generally higher DAC privileged mounter, to prevent an attack vector.

We add the option to turn off override_creds in the mount options; all
subsequent operations after mount on the filesystem will be only the
caller's credentials.  The module boolean parameter and mount option
override_creds is also added as a presence check for this "feature",
existence of /sys/module/overlay/parameters/overlay_creds

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: linux-unionfs@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Steve French <sfrench@samba.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Jan Kara <jack@suse.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mike Marshall <hubcap@omnibond.com>
Cc: Martin Brandenburg <martin@omnibond.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Cc: Hugh Dickins <hughd@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: v9fs-developer@lists.sourceforge.net
Cc: linux-afs@lists.infradead.org
Cc: linux-btrfs@vger.kernel.org
Cc: ceph-devel@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: ecryptfs@vger.kernel.org
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: linux-fsdevel@vger.kernel.org
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: devel@lists.orangefs.org
Cc: reiserfs-devel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: netdev@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: stable@vger.kernel.org # 4.4, 4.9, 4.14 & 4.19
---
v13:
- add flags argument to __vfs_getxattr
- drop GFP_NOFS side-effect

v12:
- Restore squished out patch 2 and 3 in the series,
  then change algorithm to add flags argument.
  Per-thread flag is a large security surface.

v11:
- Squish out v10 introduced patch 2 and 3 in the series,
  then and use per-thread flag instead for nesting.
- Switch name to ovl_do_vds_getxattr for __vds_getxattr wrapper.
- Add sb argument to ovl_revert_creds to match future work.

v10:
- Return NULL on CAP_DAC_READ_SEARCH
- Add __get xattr method to solve sepolicy logging issue
- Drop unnecessary sys_admin sepolicy checking for administrative
  driver internal xattr functions.

v6:
- Drop CONFIG_OVERLAY_FS_OVERRIDE_CREDS.
- Do better with the documentation, drop rationalizations.
- pr_warn message adjusted to report consequences.

v5:
- beefed up the caveats in the Documentation
- Is dependent on
  "overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh"
  "overlayfs: check CAP_MKNOD before issuing vfs_whiteout"
- Added prwarn when override_creds=off

v4:
- spelling and grammar errors in text

v3:
- Change name from caller_credentials / creator_credentials to the
  boolean override_creds.
- Changed from creator to mounter credentials.
- Updated and fortified the documentation.
- Added CONFIG_OVERLAY_FS_OVERRIDE_CREDS

v2:
- Forward port changed attr to stat, resulting in a build error.
- altered commit message.


_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply	[flat|nested] 7+ messages in thread

* [f2fs-dev] [PATCH v13 1/5] overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh
  2019-07-31 16:57 [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel
@ 2019-07-31 16:57 ` Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 2/5] Add flags option to get xattr method paired to __vfs_getxattr Mark Salyzyn via Linux-f2fs-devel
                   ` (4 subsequent siblings)
  5 siblings, 0 replies; 7+ messages in thread
From: Mark Salyzyn via Linux-f2fs-devel @ 2019-07-31 16:57 UTC (permalink / raw)
  To: linux-kernel
  Cc: Latchesar Ionkov, Dave Kleikamp, jfs-discussion, Randy Dunlap,
	linux-doc, Martin Brandenburg, samba-technical,
	Dominique Martinet, Amir Goldstein, David Howells, Chris Mason,
	David S . Miller, Andreas Dilger, ocfs2-devel, netdev,
	Tyler Hicks, linux-afs, Mike Marshall, linux-xfs,
	Andreas Gruenbacher, Sage Weil, Jonathan Corbet,
	Richard Weinberger, Mark Fasheh, devel, Hugh Dickins,
	linux-security-module, cluster-devel, Vyacheslav Dubeyko,
	v9fs-developer, Ilya Dryomov, linux-ext4, Stephen Smalley,
	linux-mm, Vivek Goyal, linux-cifs, Eric Van Hensbergen, ecryptfs,
	Josef Bacik, Darrick J . Wong, reiserfs-devel, Tejun Heo,
	Greg Kroah-Hartman, Joel Becker, linux-mtd, David Sterba,
	Jaegeuk Kim, ceph-devel, Trond Myklebust, linux-nfs,
	linux-f2fs-devel, Theodore Ts\'o, linux-fsdevel, Joseph Qi,
	Mathieu Malaterre, kernel-team, Miklos Szeredi, Jeff Layton,
	linux-unionfs, stable, Mark Salyzyn, Steve French,
	Ernesto A . Fernández, Eric W . Biederman, Jan Kara,
	Bob Peterson, Phillip Lougher, Andrew Morton, David Woodhouse,
	Anna Schumaker, linux-btrfs, Alexander Viro

Assumption never checked, should fail if the mounter creds are not
sufficient.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: linux-unionfs@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Steve French <sfrench@samba.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Jan Kara <jack@suse.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mike Marshall <hubcap@omnibond.com>
Cc: Martin Brandenburg <martin@omnibond.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Cc: Hugh Dickins <hughd@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: v9fs-developer@lists.sourceforge.net
Cc: linux-afs@lists.infradead.org
Cc: linux-btrfs@vger.kernel.org
Cc: ceph-devel@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: ecryptfs@vger.kernel.org
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: linux-fsdevel@vger.kernel.org
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: devel@lists.orangefs.org
Cc: reiserfs-devel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: netdev@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: stable@vger.kernel.org # 4.4, 4.9, 4.14 & 4.19
---
v11 + v12 + v13 - rebase

v10:
- return NULL rather than ERR_PTR(-EPERM)
- did _not_ add it ovl_can_decode_fh() because of changes since last
  review, suspect needs to be added to ovl_lower_uuid_ok()?

v8 + v9:
- rebase

v7:
- This time for realz

v6:
- rebase

v5:
- dependency of "overlayfs: override_creds=off option bypass creator_cred"
---
 fs/overlayfs/namei.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index e9717c2f7d45..9702f0d5309d 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -161,6 +161,9 @@ struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,
 	if (!uuid_equal(&fh->uuid, &mnt->mnt_sb->s_uuid))
 		return NULL;
 
+	if (!capable(CAP_DAC_READ_SEARCH))
+		return NULL;
+
 	bytes = (fh->len - offsetof(struct ovl_fh, fid));
 	real = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
 				  bytes >> 2, (int)fh->type,
-- 
2.22.0.770.g0f2c4a37fd-goog



_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply	[flat|nested] 7+ messages in thread

* [f2fs-dev] [PATCH v13 2/5] Add flags option to get xattr method paired to __vfs_getxattr
  2019-07-31 16:57 [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 1/5] overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh Mark Salyzyn via Linux-f2fs-devel
@ 2019-07-31 16:57 ` Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 3/5] overlayfs: handle XATTR_NOSECURITY flag for get xattr method Mark Salyzyn via Linux-f2fs-devel
                   ` (3 subsequent siblings)
  5 siblings, 0 replies; 7+ messages in thread
From: Mark Salyzyn via Linux-f2fs-devel @ 2019-07-31 16:57 UTC (permalink / raw)
  To: linux-kernel
  Cc: Latchesar Ionkov, Dave Kleikamp, jfs-discussion, Randy Dunlap,
	linux-integrity, linux-doc, Martin Brandenburg, samba-technical,
	Dominique Martinet, Amir Goldstein, Mimi Zohar, James Morris,
	David Howells, Chris Mason, David S . Miller, Andreas Dilger,
	ocfs2-devel, Eric Paris, netdev, Tyler Hicks, linux-afs,
	Mike Marshall, linux-xfs, Andreas Gruenbacher, Sage Weil,
	Jonathan Corbet, Richard Weinberger, Mark Fasheh, devel,
	Hugh Dickins, linux-security-module, cluster-devel, selinux,
	Vyacheslav Dubeyko, Casey Schaufler, v9fs-developer,
	Ilya Dryomov, linux-ext4, Stephen Smalley, linux-mm, Vivek Goyal,
	Serge Hallyn, linux-cifs, Eric Van Hensbergen, ecryptfs,
	Josef Bacik, Darrick J . Wong, reiserfs-devel, Tejun Heo,
	Greg Kroah-Hartman, Joel Becker, linux-mtd, David Sterba,
	Jaegeuk Kim, ceph-devel, Trond Myklebust, Paul Moore, linux-nfs,
	linux-f2fs-devel, Theodore Ts\'o, linux-fsdevel, Joseph Qi,
	Mathieu Malaterre, kernel-team, Miklos Szeredi, Jeff Layton,
	linux-unionfs, stable, Mark Salyzyn, Steve French,
	Ernesto A . Fernández, Eric W . Biederman, Jan Kara,
	Bob Peterson, Phillip Lougher, Andrew Morton, David Woodhouse,
	Anna Schumaker, linux-btrfs, Alexander Viro

Add a flag option to get xattr method that could have a bit flag of
XATTR_NOSECURITY passed to it.  XATTR_NOSECURITY is generally then
set in the __vfs_getxattr path.

This handles the case of a union filesystem driver that is being
requested by the security layer to report back the data that is the
target label or context embedded into wrapped filesystem's xattr.

For the use case where access is to be blocked by the security layer.

The path then could be security(dentry) ->
__vfs_getxattr(dentry...XATTR_NOSECUIRTY) ->
handler->get(dentry...XATTR_NOSECURITY) ->
__vfs_getxattr(lower_dentry...XATTR_NOSECUIRTY) ->
lower_handler->get(lower_dentry...XATTR_NOSECUIRTY)
which would report back through the chain data and success as
expected, but the logging security layer at the top would have the
data to determine the access permissions and report back the target
context that was blocked.

Without the get handler flag, the path on a union filesystem would be
the errant security(dentry) -> __vfs_getxattr(dentry) ->
handler->get(dentry) -> vfs_getxattr(lower_dentry) -> nested ->
security(lower_dentry, log off) -> lower_handler->get(lower_dentry)
which would report back through the chain no data, and -EACCES.

For selinux for both cases, this would translate to a correctly
determined blocked access. In the first corrected case a correct avc
log would be reported, in the second legacy case an incorrect avc log
would be reported against an uninitialized u:object_r:unlabeled:s0
context making the logs cosmetically useless for audit2allow.

This patch series is inert and is the wide-spread addition of the
flags option for xattr functions, and a replacement of _vfs_getxattr
with __vfs_getxattr(...XATTR_NOSECURITY).

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: linux-unionfs@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Steve French <sfrench@samba.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Jan Kara <jack@suse.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mike Marshall <hubcap@omnibond.com>
Cc: Martin Brandenburg <martin@omnibond.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Cc: Hugh Dickins <hughd@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: v9fs-developer@lists.sourceforge.net
Cc: linux-afs@lists.infradead.org
Cc: linux-btrfs@vger.kernel.org
Cc: ceph-devel@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: ecryptfs@vger.kernel.org
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: linux-fsdevel@vger.kernel.org
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: devel@lists.orangefs.org
Cc: reiserfs-devel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: netdev@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: stable@vger.kernel.org # 4.4, 4.9, 4.14 & 4.19
---
v13 - added flags to __vfs_getxattr call, and moved all the security
      code from vfs_getxattr into it.

v12 - Added back to patch series as get xattr with flag option.

v11 - Squashed out of patch series and replaced with per-thread flag
      solution.

v10 - Added to patch series as __get xattr method.
---
 fs/9p/acl.c                       |  3 ++-
 fs/9p/xattr.c                     |  3 ++-
 fs/afs/xattr.c                    |  6 +++---
 fs/btrfs/xattr.c                  |  3 ++-
 fs/ceph/xattr.c                   |  3 ++-
 fs/cifs/xattr.c                   |  2 +-
 fs/ecryptfs/inode.c               |  6 ++++--
 fs/ecryptfs/mmap.c                |  2 +-
 fs/ext2/xattr_trusted.c           |  2 +-
 fs/ext2/xattr_user.c              |  2 +-
 fs/ext4/xattr_security.c          |  2 +-
 fs/ext4/xattr_trusted.c           |  2 +-
 fs/ext4/xattr_user.c              |  2 +-
 fs/f2fs/xattr.c                   |  4 ++--
 fs/fuse/xattr.c                   |  4 ++--
 fs/gfs2/xattr.c                   |  3 ++-
 fs/hfs/attr.c                     |  2 +-
 fs/hfsplus/xattr.c                |  3 ++-
 fs/hfsplus/xattr_trusted.c        |  3 ++-
 fs/hfsplus/xattr_user.c           |  3 ++-
 fs/jffs2/security.c               |  3 ++-
 fs/jffs2/xattr_trusted.c          |  3 ++-
 fs/jffs2/xattr_user.c             |  3 ++-
 fs/jfs/xattr.c                    |  5 +++--
 fs/kernfs/inode.c                 |  3 ++-
 fs/nfs/nfs4proc.c                 |  6 ++++--
 fs/ocfs2/xattr.c                  |  9 +++++---
 fs/orangefs/xattr.c               |  3 ++-
 fs/overlayfs/super.c              |  8 ++++---
 fs/posix_acl.c                    |  2 +-
 fs/reiserfs/xattr_security.c      |  3 ++-
 fs/reiserfs/xattr_trusted.c       |  3 ++-
 fs/reiserfs/xattr_user.c          |  3 ++-
 fs/squashfs/xattr.c               |  2 +-
 fs/xattr.c                        | 36 +++++++++++++++----------------
 fs/xfs/xfs_xattr.c                |  3 ++-
 include/linux/xattr.h             |  9 ++++----
 include/uapi/linux/xattr.h        |  5 +++--
 mm/shmem.c                        |  3 ++-
 net/socket.c                      |  3 ++-
 security/commoncap.c              |  6 ++++--
 security/integrity/evm/evm_main.c |  3 ++-
 security/selinux/hooks.c          | 11 ++++++----
 security/smack/smack_lsm.c        |  5 +++--
 44 files changed, 119 insertions(+), 81 deletions(-)

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 6261719f6f2a..cb14e8b312bc 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -214,7 +214,8 @@ int v9fs_acl_mode(struct inode *dir, umode_t *modep,
 
 static int v9fs_xattr_get_acl(const struct xattr_handler *handler,
 			      struct dentry *dentry, struct inode *inode,
-			      const char *name, void *buffer, size_t size)
+			      const char *name, void *buffer, size_t size,
+			      int flags)
 {
 	struct v9fs_session_info *v9ses;
 	struct posix_acl *acl;
diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index ac8ff8ca4c11..5cfa772452fd 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -139,7 +139,8 @@ ssize_t v9fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 
 static int v9fs_xattr_handler_get(const struct xattr_handler *handler,
 				  struct dentry *dentry, struct inode *inode,
-				  const char *name, void *buffer, size_t size)
+				  const char *name, void *buffer, size_t size,
+				  int flags)
 {
 	const char *full_name = xattr_full_name(handler, name);
 
diff --git a/fs/afs/xattr.c b/fs/afs/xattr.c
index 5552d034090a..e6509c21f08a 100644
--- a/fs/afs/xattr.c
+++ b/fs/afs/xattr.c
@@ -334,7 +334,7 @@ static const struct xattr_handler afs_xattr_yfs_handler = {
 static int afs_xattr_get_cell(const struct xattr_handler *handler,
 			      struct dentry *dentry,
 			      struct inode *inode, const char *name,
-			      void *buffer, size_t size)
+			      void *buffer, size_t size, int flags)
 {
 	struct afs_vnode *vnode = AFS_FS_I(inode);
 	struct afs_cell *cell = vnode->volume->cell;
@@ -361,7 +361,7 @@ static const struct xattr_handler afs_xattr_afs_cell_handler = {
 static int afs_xattr_get_fid(const struct xattr_handler *handler,
 			     struct dentry *dentry,
 			     struct inode *inode, const char *name,
-			     void *buffer, size_t size)
+			     void *buffer, size_t size, int flags)
 {
 	struct afs_vnode *vnode = AFS_FS_I(inode);
 	char text[16 + 1 + 24 + 1 + 8 + 1];
@@ -397,7 +397,7 @@ static const struct xattr_handler afs_xattr_afs_fid_handler = {
 static int afs_xattr_get_volume(const struct xattr_handler *handler,
 			      struct dentry *dentry,
 			      struct inode *inode, const char *name,
-			      void *buffer, size_t size)
+			      void *buffer, size_t size, int flags)
 {
 	struct afs_vnode *vnode = AFS_FS_I(inode);
 	const char *volname = vnode->volume->name;
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 95d9aebff2c4..1e522e145344 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -353,7 +353,8 @@ ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 
 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
 				   struct dentry *unused, struct inode *inode,
-				   const char *name, void *buffer, size_t size)
+				   const char *name, void *buffer, size_t size,
+				   int flags)
 {
 	name = xattr_full_name(handler, name);
 	return btrfs_getxattr(inode, name, buffer, size);
diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 37b458a9af3a..edb7eb9ae83e 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -1171,7 +1171,8 @@ int __ceph_setxattr(struct inode *inode, const char *name,
 
 static int ceph_get_xattr_handler(const struct xattr_handler *handler,
 				  struct dentry *dentry, struct inode *inode,
-				  const char *name, void *value, size_t size)
+				  const char *name, void *value, size_t size,
+				  int flags)
 {
 	if (!ceph_is_valid_xattr(name))
 		return -EOPNOTSUPP;
diff --git a/fs/cifs/xattr.c b/fs/cifs/xattr.c
index 9076150758d8..7f71c06ce631 100644
--- a/fs/cifs/xattr.c
+++ b/fs/cifs/xattr.c
@@ -199,7 +199,7 @@ static int cifs_creation_time_get(struct dentry *dentry, struct inode *inode,
 
 static int cifs_xattr_get(const struct xattr_handler *handler,
 			  struct dentry *dentry, struct inode *inode,
-			  const char *name, void *value, size_t size)
+			  const char *name, void *value, size_t size, int flags)
 {
 	ssize_t rc = -EOPNOTSUPP;
 	unsigned int xid;
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 18426f4855f1..c710c7533729 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -1018,7 +1018,8 @@ ecryptfs_getxattr_lower(struct dentry *lower_dentry, struct inode *lower_inode,
 		goto out;
 	}
 	inode_lock(lower_inode);
-	rc = __vfs_getxattr(lower_dentry, lower_inode, name, value, size);
+	rc = __vfs_getxattr(lower_dentry, lower_inode, name, value, size,
+			    XATTR_NOSECURITY);
 	inode_unlock(lower_inode);
 out:
 	return rc;
@@ -1103,7 +1104,8 @@ const struct inode_operations ecryptfs_main_iops = {
 
 static int ecryptfs_xattr_get(const struct xattr_handler *handler,
 			      struct dentry *dentry, struct inode *inode,
-			      const char *name, void *buffer, size_t size)
+			      const char *name, void *buffer, size_t size,
+			      int flags)
 {
 	return ecryptfs_getxattr(dentry, inode, name, buffer, size);
 }
diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index cffa0c1ec829..2362be3e3b4d 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -422,7 +422,7 @@ static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 	}
 	inode_lock(lower_inode);
 	size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
-			      xattr_virt, PAGE_SIZE);
+			      xattr_virt, PAGE_SIZE, XATTR_NOSECURITY);
 	if (size < 0)
 		size = 8;
 	put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
diff --git a/fs/ext2/xattr_trusted.c b/fs/ext2/xattr_trusted.c
index 49add1107850..8d313664f0fa 100644
--- a/fs/ext2/xattr_trusted.c
+++ b/fs/ext2/xattr_trusted.c
@@ -18,7 +18,7 @@ ext2_xattr_trusted_list(struct dentry *dentry)
 static int
 ext2_xattr_trusted_get(const struct xattr_handler *handler,
 		       struct dentry *unused, struct inode *inode,
-		       const char *name, void *buffer, size_t size)
+		       const char *name, void *buffer, size_t size, int flags)
 {
 	return ext2_xattr_get(inode, EXT2_XATTR_INDEX_TRUSTED, name,
 			      buffer, size);
diff --git a/fs/ext2/xattr_user.c b/fs/ext2/xattr_user.c
index c243a3b4d69d..712b7c95cc64 100644
--- a/fs/ext2/xattr_user.c
+++ b/fs/ext2/xattr_user.c
@@ -20,7 +20,7 @@ ext2_xattr_user_list(struct dentry *dentry)
 static int
 ext2_xattr_user_get(const struct xattr_handler *handler,
 		    struct dentry *unused, struct inode *inode,
-		    const char *name, void *buffer, size_t size)
+		    const char *name, void *buffer, size_t size, int flags)
 {
 	if (!test_opt(inode->i_sb, XATTR_USER))
 		return -EOPNOTSUPP;
diff --git a/fs/ext4/xattr_security.c b/fs/ext4/xattr_security.c
index 197a9d8a15ef..50fb71393fb6 100644
--- a/fs/ext4/xattr_security.c
+++ b/fs/ext4/xattr_security.c
@@ -15,7 +15,7 @@
 static int
 ext4_xattr_security_get(const struct xattr_handler *handler,
 			struct dentry *unused, struct inode *inode,
-			const char *name, void *buffer, size_t size)
+			const char *name, void *buffer, size_t size, int flags)
 {
 	return ext4_xattr_get(inode, EXT4_XATTR_INDEX_SECURITY,
 			      name, buffer, size);
diff --git a/fs/ext4/xattr_trusted.c b/fs/ext4/xattr_trusted.c
index e9389e5d75c3..64bd8f86c1f1 100644
--- a/fs/ext4/xattr_trusted.c
+++ b/fs/ext4/xattr_trusted.c
@@ -22,7 +22,7 @@ ext4_xattr_trusted_list(struct dentry *dentry)
 static int
 ext4_xattr_trusted_get(const struct xattr_handler *handler,
 		       struct dentry *unused, struct inode *inode,
-		       const char *name, void *buffer, size_t size)
+		       const char *name, void *buffer, size_t size, int flags)
 {
 	return ext4_xattr_get(inode, EXT4_XATTR_INDEX_TRUSTED,
 			      name, buffer, size);
diff --git a/fs/ext4/xattr_user.c b/fs/ext4/xattr_user.c
index d4546184b34b..b7301373820e 100644
--- a/fs/ext4/xattr_user.c
+++ b/fs/ext4/xattr_user.c
@@ -21,7 +21,7 @@ ext4_xattr_user_list(struct dentry *dentry)
 static int
 ext4_xattr_user_get(const struct xattr_handler *handler,
 		    struct dentry *unused, struct inode *inode,
-		    const char *name, void *buffer, size_t size)
+		    const char *name, void *buffer, size_t size, int flags)
 {
 	if (!test_opt(inode->i_sb, XATTR_USER))
 		return -EOPNOTSUPP;
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index b32c45621679..76559da8dfba 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -24,7 +24,7 @@
 
 static int f2fs_xattr_generic_get(const struct xattr_handler *handler,
 		struct dentry *unused, struct inode *inode,
-		const char *name, void *buffer, size_t size)
+		const char *name, void *buffer, size_t size, int flags)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 
@@ -79,7 +79,7 @@ static bool f2fs_xattr_trusted_list(struct dentry *dentry)
 
 static int f2fs_xattr_advise_get(const struct xattr_handler *handler,
 		struct dentry *unused, struct inode *inode,
-		const char *name, void *buffer, size_t size)
+		const char *name, void *buffer, size_t size, int flags)
 {
 	if (buffer)
 		*((char *)buffer) = F2FS_I(inode)->i_advise;
diff --git a/fs/fuse/xattr.c b/fs/fuse/xattr.c
index 433717640f78..d1ef7808304e 100644
--- a/fs/fuse/xattr.c
+++ b/fs/fuse/xattr.c
@@ -176,7 +176,7 @@ int fuse_removexattr(struct inode *inode, const char *name)
 
 static int fuse_xattr_get(const struct xattr_handler *handler,
 			 struct dentry *dentry, struct inode *inode,
-			 const char *name, void *value, size_t size)
+			 const char *name, void *value, size_t size, int flags)
 {
 	return fuse_getxattr(inode, name, value, size);
 }
@@ -199,7 +199,7 @@ static bool no_xattr_list(struct dentry *dentry)
 
 static int no_xattr_get(const struct xattr_handler *handler,
 			struct dentry *dentry, struct inode *inode,
-			const char *name, void *value, size_t size)
+			const char *name, void *value, size_t size, int flags)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/fs/gfs2/xattr.c b/fs/gfs2/xattr.c
index bbe593d16bea..a9db067a99c1 100644
--- a/fs/gfs2/xattr.c
+++ b/fs/gfs2/xattr.c
@@ -588,7 +588,8 @@ static int __gfs2_xattr_get(struct inode *inode, const char *name,
 
 static int gfs2_xattr_get(const struct xattr_handler *handler,
 			  struct dentry *unused, struct inode *inode,
-			  const char *name, void *buffer, size_t size)
+			  const char *name, void *buffer, size_t size,
+			  int flags)
 {
 	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_holder gh;
diff --git a/fs/hfs/attr.c b/fs/hfs/attr.c
index 74fa62643136..08222a9c5d31 100644
--- a/fs/hfs/attr.c
+++ b/fs/hfs/attr.c
@@ -115,7 +115,7 @@ static ssize_t __hfs_getxattr(struct inode *inode, enum hfs_xattr_type type,
 
 static int hfs_xattr_get(const struct xattr_handler *handler,
 			 struct dentry *unused, struct inode *inode,
-			 const char *name, void *value, size_t size)
+			 const char *name, void *value, size_t size, int flags)
 {
 	return __hfs_getxattr(inode, handler->flags, value, size);
 }
diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
index bb0b27d88e50..381c2aaedbc8 100644
--- a/fs/hfsplus/xattr.c
+++ b/fs/hfsplus/xattr.c
@@ -839,7 +839,8 @@ static int hfsplus_removexattr(struct inode *inode, const char *name)
 
 static int hfsplus_osx_getxattr(const struct xattr_handler *handler,
 				struct dentry *unused, struct inode *inode,
-				const char *name, void *buffer, size_t size)
+				const char *name, void *buffer, size_t size,
+				int flags)
 {
 	/*
 	 * Don't allow retrieving properly prefixed attributes
diff --git a/fs/hfsplus/xattr_trusted.c b/fs/hfsplus/xattr_trusted.c
index fbad91e1dada..54d926314f8c 100644
--- a/fs/hfsplus/xattr_trusted.c
+++ b/fs/hfsplus/xattr_trusted.c
@@ -14,7 +14,8 @@
 
 static int hfsplus_trusted_getxattr(const struct xattr_handler *handler,
 				    struct dentry *unused, struct inode *inode,
-				    const char *name, void *buffer, size_t size)
+				    const char *name, void *buffer,
+				    size_t size, int flags)
 {
 	return hfsplus_getxattr(inode, name, buffer, size,
 				XATTR_TRUSTED_PREFIX,
diff --git a/fs/hfsplus/xattr_user.c b/fs/hfsplus/xattr_user.c
index 74d19faf255e..4d2b1ffff887 100644
--- a/fs/hfsplus/xattr_user.c
+++ b/fs/hfsplus/xattr_user.c
@@ -14,7 +14,8 @@
 
 static int hfsplus_user_getxattr(const struct xattr_handler *handler,
 				 struct dentry *unused, struct inode *inode,
-				 const char *name, void *buffer, size_t size)
+				 const char *name, void *buffer, size_t size,
+				 int flags)
 {
 
 	return hfsplus_getxattr(inode, name, buffer, size,
diff --git a/fs/jffs2/security.c b/fs/jffs2/security.c
index c2332e30f218..e6f42fe435af 100644
--- a/fs/jffs2/security.c
+++ b/fs/jffs2/security.c
@@ -50,7 +50,8 @@ int jffs2_init_security(struct inode *inode, struct inode *dir,
 /* ---- XATTR Handler for "security.*" ----------------- */
 static int jffs2_security_getxattr(const struct xattr_handler *handler,
 				   struct dentry *unused, struct inode *inode,
-				   const char *name, void *buffer, size_t size)
+				   const char *name, void *buffer, size_t size,
+				   int flags)
 {
 	return do_jffs2_getxattr(inode, JFFS2_XPREFIX_SECURITY,
 				 name, buffer, size);
diff --git a/fs/jffs2/xattr_trusted.c b/fs/jffs2/xattr_trusted.c
index 5d6030826c52..9dccaae549f5 100644
--- a/fs/jffs2/xattr_trusted.c
+++ b/fs/jffs2/xattr_trusted.c
@@ -18,7 +18,8 @@
 
 static int jffs2_trusted_getxattr(const struct xattr_handler *handler,
 				  struct dentry *unused, struct inode *inode,
-				  const char *name, void *buffer, size_t size)
+				  const char *name, void *buffer, size_t size,
+				  int flags)
 {
 	return do_jffs2_getxattr(inode, JFFS2_XPREFIX_TRUSTED,
 				 name, buffer, size);
diff --git a/fs/jffs2/xattr_user.c b/fs/jffs2/xattr_user.c
index 9d027b4abcf9..c0983a3e810b 100644
--- a/fs/jffs2/xattr_user.c
+++ b/fs/jffs2/xattr_user.c
@@ -18,7 +18,8 @@
 
 static int jffs2_user_getxattr(const struct xattr_handler *handler,
 			       struct dentry *unused, struct inode *inode,
-			       const char *name, void *buffer, size_t size)
+			       const char *name, void *buffer, size_t size,
+			       int flags)
 {
 	return do_jffs2_getxattr(inode, JFFS2_XPREFIX_USER,
 				 name, buffer, size);
diff --git a/fs/jfs/xattr.c b/fs/jfs/xattr.c
index db41e7803163..5c79a35bf62f 100644
--- a/fs/jfs/xattr.c
+++ b/fs/jfs/xattr.c
@@ -925,7 +925,7 @@ static int __jfs_xattr_set(struct inode *inode, const char *name,
 
 static int jfs_xattr_get(const struct xattr_handler *handler,
 			 struct dentry *unused, struct inode *inode,
-			 const char *name, void *value, size_t size)
+			 const char *name, void *value, size_t size, int flags)
 {
 	name = xattr_full_name(handler, name);
 	return __jfs_getxattr(inode, name, value, size);
@@ -942,7 +942,8 @@ static int jfs_xattr_set(const struct xattr_handler *handler,
 
 static int jfs_xattr_get_os2(const struct xattr_handler *handler,
 			     struct dentry *unused, struct inode *inode,
-			     const char *name, void *value, size_t size)
+			     const char *name, void *value, size_t size,
+			     int flags)
 {
 	if (is_known_namespace(name))
 		return -EOPNOTSUPP;
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index f3f3984cce80..89db24ce644e 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -309,7 +309,8 @@ int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
 
 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
 				struct dentry *unused, struct inode *inode,
-				const char *suffix, void *value, size_t size)
+				const char *suffix, void *value, size_t size,
+				int flags)
 {
 	const char *name = xattr_full_name(handler, suffix);
 	struct kernfs_node *kn = inode->i_private;
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 39896afc6edf..5e6a58685cd0 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7203,7 +7203,8 @@ static int nfs4_xattr_set_nfs4_acl(const struct xattr_handler *handler,
 
 static int nfs4_xattr_get_nfs4_acl(const struct xattr_handler *handler,
 				   struct dentry *unused, struct inode *inode,
-				   const char *key, void *buf, size_t buflen)
+				   const char *key, void *buf, size_t buflen,
+				   int flags)
 {
 	return nfs4_proc_get_acl(inode, buf, buflen);
 }
@@ -7228,7 +7229,8 @@ static int nfs4_xattr_set_nfs4_label(const struct xattr_handler *handler,
 
 static int nfs4_xattr_get_nfs4_label(const struct xattr_handler *handler,
 				     struct dentry *unused, struct inode *inode,
-				     const char *key, void *buf, size_t buflen)
+				     const char *key, void *buf, size_t buflen,
+				     int flags)
 {
 	if (security_ismaclabel(key))
 		return nfs4_get_security_label(inode, buf, buflen);
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 385f3aaa2448..06e615642422 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -7245,7 +7245,8 @@ int ocfs2_init_security_and_acl(struct inode *dir,
  */
 static int ocfs2_xattr_security_get(const struct xattr_handler *handler,
 				    struct dentry *unused, struct inode *inode,
-				    const char *name, void *buffer, size_t size)
+				    const char *name, void *buffer, size_t size,
+				    int flags)
 {
 	return ocfs2_xattr_get(inode, OCFS2_XATTR_INDEX_SECURITY,
 			       name, buffer, size);
@@ -7317,7 +7318,8 @@ const struct xattr_handler ocfs2_xattr_security_handler = {
  */
 static int ocfs2_xattr_trusted_get(const struct xattr_handler *handler,
 				   struct dentry *unused, struct inode *inode,
-				   const char *name, void *buffer, size_t size)
+				   const char *name, void *buffer, size_t size,
+				   int flags)
 {
 	return ocfs2_xattr_get(inode, OCFS2_XATTR_INDEX_TRUSTED,
 			       name, buffer, size);
@@ -7343,7 +7345,8 @@ const struct xattr_handler ocfs2_xattr_trusted_handler = {
  */
 static int ocfs2_xattr_user_get(const struct xattr_handler *handler,
 				struct dentry *unused, struct inode *inode,
-				const char *name, void *buffer, size_t size)
+				const char *name, void *buffer, size_t size,
+				int flags)
 {
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 
diff --git a/fs/orangefs/xattr.c b/fs/orangefs/xattr.c
index bdc285aea360..ef4180bff7bb 100644
--- a/fs/orangefs/xattr.c
+++ b/fs/orangefs/xattr.c
@@ -541,7 +541,8 @@ static int orangefs_xattr_get_default(const struct xattr_handler *handler,
 				      struct inode *inode,
 				      const char *name,
 				      void *buffer,
-				      size_t size)
+				      size_t size,
+				      int flags)
 {
 	return orangefs_inode_getxattr(inode, name, buffer, size);
 
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index b368e2e102fa..a7b21f2ea2dd 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -854,7 +854,7 @@ static unsigned int ovl_split_lowerdirs(char *str)
 static int __maybe_unused
 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
 			struct dentry *dentry, struct inode *inode,
-			const char *name, void *buffer, size_t size)
+			const char *name, void *buffer, size_t size, int flags)
 {
 	return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
 }
@@ -919,7 +919,8 @@ ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 
 static int ovl_own_xattr_get(const struct xattr_handler *handler,
 			     struct dentry *dentry, struct inode *inode,
-			     const char *name, void *buffer, size_t size)
+			     const char *name, void *buffer, size_t size,
+			     int flags)
 {
 	return -EOPNOTSUPP;
 }
@@ -934,7 +935,8 @@ static int ovl_own_xattr_set(const struct xattr_handler *handler,
 
 static int ovl_other_xattr_get(const struct xattr_handler *handler,
 			       struct dentry *dentry, struct inode *inode,
-			       const char *name, void *buffer, size_t size)
+			       const char *name, void *buffer, size_t size,
+			       int flags)
 {
 	return ovl_xattr_get(dentry, inode, name, buffer, size);
 }
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 84ad1c90d535..cd55621e570b 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -832,7 +832,7 @@ EXPORT_SYMBOL (posix_acl_to_xattr);
 static int
 posix_acl_xattr_get(const struct xattr_handler *handler,
 		    struct dentry *unused, struct inode *inode,
-		    const char *name, void *value, size_t size)
+		    const char *name, void *value, size_t size, int flags)
 {
 	struct posix_acl *acl;
 	int error;
diff --git a/fs/reiserfs/xattr_security.c b/fs/reiserfs/xattr_security.c
index 20be9a0e5870..eedfa07a4fd0 100644
--- a/fs/reiserfs/xattr_security.c
+++ b/fs/reiserfs/xattr_security.c
@@ -11,7 +11,8 @@
 
 static int
 security_get(const struct xattr_handler *handler, struct dentry *unused,
-	     struct inode *inode, const char *name, void *buffer, size_t size)
+	     struct inode *inode, const char *name, void *buffer, size_t size,
+	     int flags)
 {
 	if (IS_PRIVATE(inode))
 		return -EPERM;
diff --git a/fs/reiserfs/xattr_trusted.c b/fs/reiserfs/xattr_trusted.c
index 5ed48da3d02b..2d11d98605dd 100644
--- a/fs/reiserfs/xattr_trusted.c
+++ b/fs/reiserfs/xattr_trusted.c
@@ -10,7 +10,8 @@
 
 static int
 trusted_get(const struct xattr_handler *handler, struct dentry *unused,
-	    struct inode *inode, const char *name, void *buffer, size_t size)
+	    struct inode *inode, const char *name, void *buffer, size_t size,
+	    int flags)
 {
 	if (!capable(CAP_SYS_ADMIN) || IS_PRIVATE(inode))
 		return -EPERM;
diff --git a/fs/reiserfs/xattr_user.c b/fs/reiserfs/xattr_user.c
index a573ca45bacc..2a59d85c69c9 100644
--- a/fs/reiserfs/xattr_user.c
+++ b/fs/reiserfs/xattr_user.c
@@ -9,7 +9,8 @@
 
 static int
 user_get(const struct xattr_handler *handler, struct dentry *unused,
-	 struct inode *inode, const char *name, void *buffer, size_t size)
+	 struct inode *inode, const char *name, void *buffer, size_t size,
+	 int flags)
 {
 	if (!reiserfs_xattrs_user(inode->i_sb))
 		return -EOPNOTSUPP;
diff --git a/fs/squashfs/xattr.c b/fs/squashfs/xattr.c
index e1e3f3dd5a06..d8d58c990652 100644
--- a/fs/squashfs/xattr.c
+++ b/fs/squashfs/xattr.c
@@ -204,7 +204,7 @@ static int squashfs_xattr_handler_get(const struct xattr_handler *handler,
 				      struct dentry *unused,
 				      struct inode *inode,
 				      const char *name,
-				      void *buffer, size_t size)
+				      void *buffer, size_t size, int flags)
 {
 	return squashfs_xattr_get(inode, handler->flags, name,
 		buffer, size);
diff --git a/fs/xattr.c b/fs/xattr.c
index 90dd78f0eb27..71f887518d6f 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -281,7 +281,7 @@ vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 		return PTR_ERR(handler);
 	if (!handler->get)
 		return -EOPNOTSUPP;
-	error = handler->get(handler, dentry, inode, name, NULL, 0);
+	error = handler->get(handler, dentry, inode, name, NULL, 0, 0);
 	if (error < 0)
 		return error;
 
@@ -292,32 +292,20 @@ vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 		memset(value, 0, error + 1);
 	}
 
-	error = handler->get(handler, dentry, inode, name, value, error);
+	error = handler->get(handler, dentry, inode, name, value, error, 0);
 	*xattr_value = value;
 	return error;
 }
 
 ssize_t
 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
-	       void *value, size_t size)
+	       void *value, size_t size, int flags)
 {
 	const struct xattr_handler *handler;
-
-	handler = xattr_resolve_name(inode, &name);
-	if (IS_ERR(handler))
-		return PTR_ERR(handler);
-	if (!handler->get)
-		return -EOPNOTSUPP;
-	return handler->get(handler, dentry, inode, name, value, size);
-}
-EXPORT_SYMBOL(__vfs_getxattr);
-
-ssize_t
-vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
-{
-	struct inode *inode = dentry->d_inode;
 	int error;
 
+	if (flags & XATTR_NOSECURITY)
+		goto nolsm;
 	error = xattr_permission(inode, name, MAY_READ);
 	if (error)
 		return error;
@@ -339,7 +327,19 @@ vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 		return ret;
 	}
 nolsm:
-	return __vfs_getxattr(dentry, inode, name, value, size);
+	handler = xattr_resolve_name(inode, &name);
+	if (IS_ERR(handler))
+		return PTR_ERR(handler);
+	if (!handler->get)
+		return -EOPNOTSUPP;
+	return handler->get(handler, dentry, inode, name, value, size, flags);
+}
+EXPORT_SYMBOL(__vfs_getxattr);
+
+ssize_t
+vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
+{
+	return __vfs_getxattr(dentry, dentry->d_inode, name, value, size, 0);
 }
 EXPORT_SYMBOL_GPL(vfs_getxattr);
 
diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
index 3123b5aaad2a..cafc99c48e20 100644
--- a/fs/xfs/xfs_xattr.c
+++ b/fs/xfs/xfs_xattr.c
@@ -18,7 +18,8 @@
 
 static int
 xfs_xattr_get(const struct xattr_handler *handler, struct dentry *unused,
-		struct inode *inode, const char *name, void *value, size_t size)
+		struct inode *inode, const char *name, void *value, size_t size,
+		int flags)
 {
 	int xflags = handler->flags;
 	struct xfs_inode *ip = XFS_I(inode);
diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index 6dad031be3c2..e5c191b30818 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -30,10 +30,10 @@ struct xattr_handler {
 	const char *prefix;
 	int flags;      /* fs private flags */
 	bool (*list)(struct dentry *dentry);
-	int (*get)(const struct xattr_handler *, struct dentry *dentry,
+	int (*get)(const struct xattr_handler *handler, struct dentry *dentry,
 		   struct inode *inode, const char *name, void *buffer,
-		   size_t size);
-	int (*set)(const struct xattr_handler *, struct dentry *dentry,
+		   size_t size, int flags);
+	int (*set)(const struct xattr_handler *handler, struct dentry *dentry,
 		   struct inode *inode, const char *name, const void *buffer,
 		   size_t size, int flags);
 };
@@ -46,7 +46,8 @@ struct xattr {
 	size_t value_len;
 };
 
-ssize_t __vfs_getxattr(struct dentry *, struct inode *, const char *, void *, size_t);
+ssize_t __vfs_getxattr(struct dentry *, struct inode *, const char *, void *,
+		       size_t, int);
 ssize_t vfs_getxattr(struct dentry *, const char *, void *, size_t);
 ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
 int __vfs_setxattr(struct dentry *, struct inode *, const char *, const void *, size_t, int);
diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h
index c1395b5bd432..1216d777d210 100644
--- a/include/uapi/linux/xattr.h
+++ b/include/uapi/linux/xattr.h
@@ -17,8 +17,9 @@
 #if __UAPI_DEF_XATTR
 #define __USE_KERNEL_XATTR_DEFS
 
-#define XATTR_CREATE	0x1	/* set value, fail if attr already exists */
-#define XATTR_REPLACE	0x2	/* set value, fail if attr does not exist */
+#define XATTR_CREATE	 0x1	/* set value, fail if attr already exists */
+#define XATTR_REPLACE	 0x2	/* set value, fail if attr does not exist */
+#define XATTR_NOSECURITY 0x4	/* get value, do not involve security check */
 #endif
 
 /* Namespaces */
diff --git a/mm/shmem.c b/mm/shmem.c
index 626d8c74b973..34d3818b4424 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3206,7 +3206,8 @@ static int shmem_initxattrs(struct inode *inode,
 
 static int shmem_xattr_handler_get(const struct xattr_handler *handler,
 				   struct dentry *unused, struct inode *inode,
-				   const char *name, void *buffer, size_t size)
+				   const char *name, void *buffer, size_t size,
+				   int flags)
 {
 	struct shmem_inode_info *info = SHMEM_I(inode);
 
diff --git a/net/socket.c b/net/socket.c
index 6a9ab7a8b1d2..6b0fea92dd02 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -300,7 +300,8 @@ static const struct dentry_operations sockfs_dentry_operations = {
 
 static int sockfs_xattr_get(const struct xattr_handler *handler,
 			    struct dentry *dentry, struct inode *inode,
-			    const char *suffix, void *value, size_t size)
+			    const char *suffix, void *value, size_t size,
+			    int flags)
 {
 	if (value) {
 		if (dentry->d_name.len + 1 > size)
diff --git a/security/commoncap.c b/security/commoncap.c
index f4ee0ae106b2..378a2f66a73d 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -297,7 +297,8 @@ int cap_inode_need_killpriv(struct dentry *dentry)
 	struct inode *inode = d_backing_inode(dentry);
 	int error;
 
-	error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
+	error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0,
+			       XATTR_NOSECURITY);
 	return error > 0;
 }
 
@@ -586,7 +587,8 @@ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data
 
 	fs_ns = inode->i_sb->s_user_ns;
 	size = __vfs_getxattr((struct dentry *)dentry, inode,
-			      XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
+			      XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ,
+			      XATTR_NOSECURITY);
 	if (size == -ENODATA || size == -EOPNOTSUPP)
 		/* no data, that's ok */
 		return -ENODATA;
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index f9a81b187fae..921c8f2afcaf 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -100,7 +100,8 @@ static int evm_find_protected_xattrs(struct dentry *dentry)
 		return -EOPNOTSUPP;
 
 	list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
-		error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
+		error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0,
+				       XATTR_NOSECURITY);
 		if (error < 0) {
 			if (error == -ENODATA)
 				continue;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 74dd46de01b6..b0822da0658f 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -552,7 +552,8 @@ static int sb_finish_set_opts(struct super_block *sb)
 			goto out;
 		}
 
-		rc = __vfs_getxattr(root, root_inode, XATTR_NAME_SELINUX, NULL, 0);
+		rc = __vfs_getxattr(root, root_inode, XATTR_NAME_SELINUX, NULL,
+				    0, XATTR_NOSECURITY);
 		if (rc < 0 && rc != -ENODATA) {
 			if (rc == -EOPNOTSUPP)
 				pr_warn("SELinux: (dev %s, type "
@@ -1378,12 +1379,14 @@ static int inode_doinit_use_xattr(struct inode *inode, struct dentry *dentry,
 		return -ENOMEM;
 
 	context[len] = '\0';
-	rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
+	rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len,
+			    XATTR_NOSECURITY);
 	if (rc == -ERANGE) {
 		kfree(context);
 
 		/* Need a larger buffer.  Query for the right size. */
-		rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, NULL, 0);
+		rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, NULL, 0,
+				    XATTR_NOSECURITY);
 		if (rc < 0)
 			return rc;
 
@@ -1394,7 +1397,7 @@ static int inode_doinit_use_xattr(struct inode *inode, struct dentry *dentry,
 
 		context[len] = '\0';
 		rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX,
-				    context, len);
+				    context, len, XATTR_NOSECURITY);
 	}
 	if (rc < 0) {
 		kfree(context);
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 4c5e5a438f8b..158b35772be1 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -292,7 +292,8 @@ static struct smack_known *smk_fetch(const char *name, struct inode *ip,
 	if (buffer == NULL)
 		return ERR_PTR(-ENOMEM);
 
-	rc = __vfs_getxattr(dp, ip, name, buffer, SMK_LONGLABEL);
+	rc = __vfs_getxattr(dp, ip, name, buffer, SMK_LONGLABEL,
+			    XATTR_NOSECURITY);
 	if (rc < 0)
 		skp = ERR_PTR(rc);
 	else if (rc == 0)
@@ -3442,7 +3443,7 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 			} else {
 				rc = __vfs_getxattr(dp, inode,
 					XATTR_NAME_SMACKTRANSMUTE, trattr,
-					TRANS_TRUE_SIZE);
+					TRANS_TRUE_SIZE, XATTR_NOSECURITY);
 				if (rc >= 0 && strncmp(trattr, TRANS_TRUE,
 						       TRANS_TRUE_SIZE) != 0)
 					rc = -EINVAL;
-- 
2.22.0.770.g0f2c4a37fd-goog



_______________________________________________
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Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply	[flat|nested] 7+ messages in thread

* [f2fs-dev] [PATCH v13 3/5] overlayfs: handle XATTR_NOSECURITY flag for get xattr method
  2019-07-31 16:57 [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 1/5] overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 2/5] Add flags option to get xattr method paired to __vfs_getxattr Mark Salyzyn via Linux-f2fs-devel
@ 2019-07-31 16:57 ` Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 4/5] overlayfs: internal getxattr operations without sepolicy checking Mark Salyzyn via Linux-f2fs-devel
                   ` (2 subsequent siblings)
  5 siblings, 0 replies; 7+ messages in thread
From: Mark Salyzyn via Linux-f2fs-devel @ 2019-07-31 16:57 UTC (permalink / raw)
  To: linux-kernel
  Cc: Latchesar Ionkov, Dave Kleikamp, jfs-discussion, Randy Dunlap,
	linux-doc, Martin Brandenburg, samba-technical,
	Dominique Martinet, Amir Goldstein, David Howells, Chris Mason,
	David S . Miller, Andreas Dilger, ocfs2-devel, netdev,
	Tyler Hicks, linux-afs, Mike Marshall, linux-xfs,
	Andreas Gruenbacher, Sage Weil, Jonathan Corbet,
	Richard Weinberger, Mark Fasheh, devel, Hugh Dickins,
	linux-security-module, cluster-devel, Vyacheslav Dubeyko,
	v9fs-developer, Ilya Dryomov, linux-ext4, Stephen Smalley,
	linux-mm, Vivek Goyal, linux-cifs, Eric Van Hensbergen, ecryptfs,
	Josef Bacik, Darrick J . Wong, reiserfs-devel, Tejun Heo,
	Greg Kroah-Hartman, Joel Becker, linux-mtd, David Sterba,
	Jaegeuk Kim, ceph-devel, Trond Myklebust, linux-nfs,
	linux-f2fs-devel, Theodore Ts\'o, linux-fsdevel, Joseph Qi,
	Mathieu Malaterre, kernel-team, Miklos Szeredi, Jeff Layton,
	linux-unionfs, stable, Mark Salyzyn, Steve French,
	Ernesto A . Fernández, Eric W . Biederman, Jan Kara,
	Bob Peterson, Phillip Lougher, Andrew Morton, David Woodhouse,
	Anna Schumaker, linux-btrfs, Alexander Viro

Because of the overlayfs getxattr recursion, the incoming inode fails
to update the selinux sid resulting in avc denials being reported
against a target context of u:object_r:unlabeled:s0.

Solution is to respond to the XATTR_NOSECURITY flag in get xattr
method that calls the __vfs_getxattr handler instead so that the
context can be read in, rather than being denied with an -EACCES
when vfs_getxattr handler is called.

For the use case where access is to be blocked by the security layer.

The path then would be security(dentry) ->
__vfs_getxattr(dentry...XATTR_NOSECURITY) ->
handler->get(dentry...XATTR_NOSECURITY) ->
__vfs_getxattr(realdentry...XATTR_NOSECURITY) ->
lower_handler->get(realdentry...XATTR_NOSECURITY) which
would report back through the chain data and success as expected,
the logging security layer at the top would have the data to
determine the access permissions and report back to the logs and
the caller that the target context was blocked.

For selinux this would solve the cosmetic issue of the selinux log
and allow audit2allow to correctly report the rule needed to address
the access problem.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: linux-unionfs@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Steve French <sfrench@samba.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Jan Kara <jack@suse.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mike Marshall <hubcap@omnibond.com>
Cc: Martin Brandenburg <martin@omnibond.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Cc: Hugh Dickins <hughd@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: v9fs-developer@lists.sourceforge.net
Cc: linux-afs@lists.infradead.org
Cc: linux-btrfs@vger.kernel.org
Cc: ceph-devel@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: ecryptfs@vger.kernel.org
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: linux-fsdevel@vger.kernel.org
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: devel@lists.orangefs.org
Cc: reiserfs-devel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: netdev@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: stable@vger.kernel.org # 4.4, 4.9, 4.14 & 4.19
---
v13 - rebase to use __vfs_getxattr flags option.

v12 - Added back to patch series as get xattr with flag option.

v11 - Squashed out of patch series and replaced with per-thread flag
      solution.

v10 - Added to patch series as __get xattr method.
---
 fs/overlayfs/inode.c     | 5 +++--
 fs/overlayfs/overlayfs.h | 2 +-
 fs/overlayfs/super.c     | 4 ++--
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 7663aeb85fa3..1bf11ae44313 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -363,7 +363,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 }
 
 int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
-		  void *value, size_t size)
+		  void *value, size_t size, int flags)
 {
 	ssize_t res;
 	const struct cred *old_cred;
@@ -371,7 +371,8 @@ int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
 		ovl_i_dentry_upper(inode) ?: ovl_dentry_lower(dentry);
 
 	old_cred = ovl_override_creds(dentry->d_sb);
-	res = vfs_getxattr(realdentry, name, value, size);
+	res = __vfs_getxattr(realdentry, d_inode(realdentry), name,
+			     value, size, flags);
 	revert_creds(old_cred);
 	return res;
 }
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 6934bcf030f0..ab3d031c422b 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -356,7 +356,7 @@ int ovl_permission(struct inode *inode, int mask);
 int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 		  const void *value, size_t size, int flags);
 int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
-		  void *value, size_t size);
+		  void *value, size_t size, int flags);
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
 struct posix_acl *ovl_get_acl(struct inode *inode, int type);
 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index a7b21f2ea2dd..6f041e1fceda 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -856,7 +856,7 @@ ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
 			struct dentry *dentry, struct inode *inode,
 			const char *name, void *buffer, size_t size, int flags)
 {
-	return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
+	return ovl_xattr_get(dentry, inode, handler->name, buffer, size, flags);
 }
 
 static int __maybe_unused
@@ -938,7 +938,7 @@ static int ovl_other_xattr_get(const struct xattr_handler *handler,
 			       const char *name, void *buffer, size_t size,
 			       int flags)
 {
-	return ovl_xattr_get(dentry, inode, name, buffer, size);
+	return ovl_xattr_get(dentry, inode, name, buffer, size, flags);
 }
 
 static int ovl_other_xattr_set(const struct xattr_handler *handler,
-- 
2.22.0.770.g0f2c4a37fd-goog



_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply	[flat|nested] 7+ messages in thread

* [f2fs-dev] [PATCH v13 4/5] overlayfs: internal getxattr operations without sepolicy checking
  2019-07-31 16:57 [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel
                   ` (2 preceding siblings ...)
  2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 3/5] overlayfs: handle XATTR_NOSECURITY flag for get xattr method Mark Salyzyn via Linux-f2fs-devel
@ 2019-07-31 16:57 ` Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:58 ` [f2fs-dev] [PATCH v13 5/5] overlayfs: override_creds=off option bypass creator_cred Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:58 ` [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel
  5 siblings, 0 replies; 7+ messages in thread
From: Mark Salyzyn via Linux-f2fs-devel @ 2019-07-31 16:57 UTC (permalink / raw)
  To: linux-kernel
  Cc: Latchesar Ionkov, Dave Kleikamp, jfs-discussion, Randy Dunlap,
	linux-doc, Martin Brandenburg, samba-technical,
	Dominique Martinet, Amir Goldstein, David Howells, Chris Mason,
	David S . Miller, Andreas Dilger, ocfs2-devel, netdev,
	Tyler Hicks, linux-afs, Mike Marshall, linux-xfs,
	Andreas Gruenbacher, Sage Weil, Jonathan Corbet,
	Richard Weinberger, Mark Fasheh, devel, Hugh Dickins,
	linux-security-module, cluster-devel, Vyacheslav Dubeyko,
	v9fs-developer, Ilya Dryomov, linux-ext4, Stephen Smalley,
	linux-mm, Vivek Goyal, linux-cifs, Eric Van Hensbergen, ecryptfs,
	Josef Bacik, Darrick J . Wong, reiserfs-devel, Tejun Heo,
	Greg Kroah-Hartman, Joel Becker, linux-mtd, David Sterba,
	Jaegeuk Kim, ceph-devel, Trond Myklebust, linux-nfs,
	linux-f2fs-devel, Theodore Ts\'o, linux-fsdevel, Joseph Qi,
	Mathieu Malaterre, kernel-team, Miklos Szeredi, Jeff Layton,
	linux-unionfs, stable, Mark Salyzyn, Steve French,
	Ernesto A . Fernández, Eric W . Biederman, Jan Kara,
	Bob Peterson, Phillip Lougher, Andrew Morton, David Woodhouse,
	Anna Schumaker, linux-btrfs, Alexander Viro

Check impure, opaque, origin & meta xattr with no sepolicy audit
(using __vfs_getxattr) since these operations are internal to
overlayfs operations and do not disclose any data.  This became
an issue for credential override off since sys_admin would have
been required by the caller; whereas would have been inherently
present for the creator since it performed the mount.

This is a change in operations since we do not check in the new
ovl_do_vfs_getxattr function if the credential override is off or
not.  Reasoning is that the sepolicy check is unnecessary overhead,
especially since the check can be expensive.

Because for override credentials off, this affects _everyone_ that
underneath performs private xattr calls without the appropriate
sepolicy permissions and sys_admin capability.  Providing blanket
support for sys_admin would be bad for all possible callers.

For the override credentials on, this will affect only the mounter,
should it lack sepolicy permissions. Not considered a security
problem since mounting by definition has sys_admin capabilities,
but sepolicy contexts would still need to be crafted.

It should be noted that there is precedence, __vfs_getxattr is used
in other filesystems for their own internal trusted xattr management.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: linux-unionfs@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Steve French <sfrench@samba.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Jan Kara <jack@suse.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mike Marshall <hubcap@omnibond.com>
Cc: Martin Brandenburg <martin@omnibond.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Cc: Hugh Dickins <hughd@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: v9fs-developer@lists.sourceforge.net
Cc: linux-afs@lists.infradead.org
Cc: linux-btrfs@vger.kernel.org
Cc: ceph-devel@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: ecryptfs@vger.kernel.org
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: linux-fsdevel@vger.kernel.org
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: devel@lists.orangefs.org
Cc: reiserfs-devel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: netdev@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: stable@vger.kernel.org # 4.4, 4.9, 4.14 & 4.19
---
v13 - rebase to use __vfs_getxattr flags option

v12 - rebase

v11 - switch name to ovl_do_vfs_getxattr, fortify comment

v10 - added to patch series
---
 fs/overlayfs/namei.c     | 12 +++++++-----
 fs/overlayfs/overlayfs.h |  2 ++
 fs/overlayfs/util.c      | 25 ++++++++++++++++---------
 3 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 9702f0d5309d..a4a452c489fa 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -106,10 +106,11 @@ int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
 
 static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name)
 {
-	int res, err;
+	ssize_t res;
+	int err;
 	struct ovl_fh *fh = NULL;
 
-	res = vfs_getxattr(dentry, name, NULL, 0);
+	res = ovl_do_vfs_getxattr(dentry, name, NULL, 0);
 	if (res < 0) {
 		if (res == -ENODATA || res == -EOPNOTSUPP)
 			return NULL;
@@ -123,7 +124,7 @@ static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name)
 	if (!fh)
 		return ERR_PTR(-ENOMEM);
 
-	res = vfs_getxattr(dentry, name, fh, res);
+	res = ovl_do_vfs_getxattr(dentry, name, fh, res);
 	if (res < 0)
 		goto fail;
 
@@ -141,10 +142,11 @@ static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name)
 	return NULL;
 
 fail:
-	pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res);
+	pr_warn_ratelimited("overlayfs: failed to get origin (%zi)\n", res);
 	goto out;
 invalid:
-	pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh);
+	pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n",
+			    (int)res, fh);
 	goto out;
 }
 
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index ab3d031c422b..9d26d8758513 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -205,6 +205,8 @@ int ovl_want_write(struct dentry *dentry);
 void ovl_drop_write(struct dentry *dentry);
 struct dentry *ovl_workdir(struct dentry *dentry);
 const struct cred *ovl_override_creds(struct super_block *sb);
+ssize_t ovl_do_vfs_getxattr(struct dentry *dentry, const char *name, void *buf,
+			    size_t size);
 struct super_block *ovl_same_sb(struct super_block *sb);
 int ovl_can_decode_fh(struct super_block *sb);
 struct dentry *ovl_indexdir(struct super_block *sb);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index f5678a3f8350..c588c0d66d8c 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -40,6 +40,13 @@ const struct cred *ovl_override_creds(struct super_block *sb)
 	return override_creds(ofs->creator_cred);
 }
 
+ssize_t ovl_do_vfs_getxattr(struct dentry *dentry, const char *name, void *buf,
+			    size_t size)
+{
+	return __vfs_getxattr(dentry, d_inode(dentry), name, buf, size,
+			      XATTR_NOSECURITY);
+}
+
 struct super_block *ovl_same_sb(struct super_block *sb)
 {
 	struct ovl_fs *ofs = sb->s_fs_info;
@@ -537,9 +544,9 @@ void ovl_copy_up_end(struct dentry *dentry)
 
 bool ovl_check_origin_xattr(struct dentry *dentry)
 {
-	int res;
+	ssize_t res;
 
-	res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
+	res = ovl_do_vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
 
 	/* Zero size value means "copied up but origin unknown" */
 	if (res >= 0)
@@ -550,13 +557,13 @@ bool ovl_check_origin_xattr(struct dentry *dentry)
 
 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
 {
-	int res;
+	ssize_t res;
 	char val;
 
 	if (!d_is_dir(dentry))
 		return false;
 
-	res = vfs_getxattr(dentry, name, &val, 1);
+	res = ovl_do_vfs_getxattr(dentry, name, &val, 1);
 	if (res == 1 && val == 'y')
 		return true;
 
@@ -837,13 +844,13 @@ int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
 /* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */
 int ovl_check_metacopy_xattr(struct dentry *dentry)
 {
-	int res;
+	ssize_t res;
 
 	/* Only regular files can have metacopy xattr */
 	if (!S_ISREG(d_inode(dentry)->i_mode))
 		return 0;
 
-	res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);
+	res = ovl_do_vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);
 	if (res < 0) {
 		if (res == -ENODATA || res == -EOPNOTSUPP)
 			return 0;
@@ -852,7 +859,7 @@ int ovl_check_metacopy_xattr(struct dentry *dentry)
 
 	return 1;
 out:
-	pr_warn_ratelimited("overlayfs: failed to get metacopy (%i)\n", res);
+	pr_warn_ratelimited("overlayfs: failed to get metacopy (%zi)\n", res);
 	return res;
 }
 
@@ -878,7 +885,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value,
 	ssize_t res;
 	char *buf = NULL;
 
-	res = vfs_getxattr(dentry, name, NULL, 0);
+	res = ovl_do_vfs_getxattr(dentry, name, NULL, 0);
 	if (res < 0) {
 		if (res == -ENODATA || res == -EOPNOTSUPP)
 			return -ENODATA;
@@ -890,7 +897,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value,
 		if (!buf)
 			return -ENOMEM;
 
-		res = vfs_getxattr(dentry, name, buf, res);
+		res = ovl_do_vfs_getxattr(dentry, name, buf, res);
 		if (res < 0)
 			goto fail;
 	}
-- 
2.22.0.770.g0f2c4a37fd-goog



_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply	[flat|nested] 7+ messages in thread

* [f2fs-dev] [PATCH v13 5/5] overlayfs: override_creds=off option bypass creator_cred
  2019-07-31 16:57 [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel
                   ` (3 preceding siblings ...)
  2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 4/5] overlayfs: internal getxattr operations without sepolicy checking Mark Salyzyn via Linux-f2fs-devel
@ 2019-07-31 16:58 ` Mark Salyzyn via Linux-f2fs-devel
  2019-07-31 16:58 ` [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel
  5 siblings, 0 replies; 7+ messages in thread
From: Mark Salyzyn via Linux-f2fs-devel @ 2019-07-31 16:58 UTC (permalink / raw)
  To: linux-kernel
  Cc: Latchesar Ionkov, Dave Kleikamp, jfs-discussion, Randy Dunlap,
	linux-doc, Martin Brandenburg, samba-technical,
	Dominique Martinet, Amir Goldstein, David Howells, Chris Mason,
	David S . Miller, Andreas Dilger, ocfs2-devel, netdev,
	Tyler Hicks, linux-afs, Mike Marshall, linux-xfs,
	Andreas Gruenbacher, Sage Weil, Jonathan Corbet,
	Richard Weinberger, Mark Fasheh, devel, Hugh Dickins,
	linux-security-module, cluster-devel, Vyacheslav Dubeyko,
	v9fs-developer, Ilya Dryomov, linux-ext4, Stephen Smalley,
	linux-mm, Vivek Goyal, linux-cifs, Eric Van Hensbergen, ecryptfs,
	Josef Bacik, Darrick J . Wong, reiserfs-devel, Tejun Heo,
	Greg Kroah-Hartman, Joel Becker, linux-mtd, David Sterba,
	Jaegeuk Kim, ceph-devel, Trond Myklebust, linux-nfs,
	linux-f2fs-devel, Theodore Ts\'o, linux-fsdevel, Joseph Qi,
	Mathieu Malaterre, kernel-team, Miklos Szeredi, Jeff Layton,
	linux-unionfs, stable, Mark Salyzyn, Steve French,
	Ernesto A . Fernández, Eric W . Biederman, Jan Kara,
	Bob Peterson, Phillip Lougher, Andrew Morton, David Woodhouse,
	Anna Schumaker, linux-btrfs, Alexander Viro

By default, all access to the upper, lower and work directories is the
recorded mounter's MAC and DAC credentials.  The incoming accesses are
checked against the caller's credentials.

If the principles of least privilege are applied, the mounter's
credentials might not overlap the credentials of the caller's when
accessing the overlayfs filesystem.  For example, a file that a lower
DAC privileged caller can execute, is MAC denied to the generally
higher DAC privileged mounter, to prevent an attack vector.

We add the option to turn off override_creds in the mount options; all
subsequent operations after mount on the filesystem will be only the
caller's credentials.  The module boolean parameter and mount option
override_creds is also added as a presence check for this "feature",
existence of /sys/module/overlay/parameters/override_creds.

It was not always this way.  Circa 4.6 there was no recorded mounter's
credentials, instead privileged access to upper or work directories
were temporarily increased to perform the operations.  The MAC
(selinux) policies were caller's in all cases.  override_creds=off
partially returns us to this older access model minus the insecure
temporary credential increases.  This is to permit use in a system
with non-overlapping security models for each executable including
the agent that mounts the overlayfs filesystem.  In Android
this is the case since init, which performs the mount operations,
has a minimal MAC set of privileges to reduce any attack surface,
and services that use the content have a different set of MAC
privileges (eg: read, for vendor labelled configuration, execute for
vendor libraries and modules).  The caveats are not a problem in
the Android usage model, however they should be fixed for
completeness and for general use in time.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: linux-unionfs@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Steve French <sfrench@samba.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Jan Kara <jack@suse.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mike Marshall <hubcap@omnibond.com>
Cc: Martin Brandenburg <martin@omnibond.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Cc: Hugh Dickins <hughd@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: v9fs-developer@lists.sourceforge.net
Cc: linux-afs@lists.infradead.org
Cc: linux-btrfs@vger.kernel.org
Cc: ceph-devel@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: ecryptfs@vger.kernel.org
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: linux-fsdevel@vger.kernel.org
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: devel@lists.orangefs.org
Cc: reiserfs-devel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: netdev@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: stable@vger.kernel.org # 4.4, 4.9, 4.14 & 4.19 NB: this is a desired feature
---
v12 + v13:
- Rebase

v11:
- add sb argument to ovl_revert_creds to match future work

v10:
- Rebase (and expand because of increased revert_cred usage)

v9:
- Add to the caveats

v8:
- drop pr_warn message after straw poll to remove it.
- added a use case in the commit message

v7:
- change name of internal parameter to ovl_override_creds_def
- report override_creds only if different than default

v6:
- Drop CONFIG_OVERLAY_FS_OVERRIDE_CREDS.
- Do better with the documentation.
- pr_warn message adjusted to report consequences.

v5:
- beefed up the caveats in the Documentation
- Is dependent on
  "overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh"
  "overlayfs: check CAP_MKNOD before issuing vfs_whiteout"
- Added prwarn when override_creds=off

v4:
- spelling and grammar errors in text

v3:
- Change name from caller_credentials / creator_credentials to the
  boolean override_creds.
- Changed from creator to mounter credentials.
- Updated and fortified the documentation.
- Added CONFIG_OVERLAY_FS_OVERRIDE_CREDS

v2:
- Forward port changed attr to stat, resulting in a build error.
- altered commit message.
---
 Documentation/filesystems/overlayfs.txt | 23 +++++++++++++++++++++++
 fs/overlayfs/copy_up.c                  |  2 +-
 fs/overlayfs/dir.c                      | 11 ++++++-----
 fs/overlayfs/file.c                     | 20 ++++++++++----------
 fs/overlayfs/inode.c                    | 18 +++++++++---------
 fs/overlayfs/namei.c                    |  6 +++---
 fs/overlayfs/overlayfs.h                |  1 +
 fs/overlayfs/ovl_entry.h                |  1 +
 fs/overlayfs/readdir.c                  |  4 ++--
 fs/overlayfs/super.c                    | 22 +++++++++++++++++++++-
 fs/overlayfs/util.c                     | 12 ++++++++++--
 11 files changed, 87 insertions(+), 33 deletions(-)

diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt
index 1da2f1668f08..d48125076602 100644
--- a/Documentation/filesystems/overlayfs.txt
+++ b/Documentation/filesystems/overlayfs.txt
@@ -102,6 +102,29 @@ Only the lists of names from directories are merged.  Other content
 such as metadata and extended attributes are reported for the upper
 directory only.  These attributes of the lower directory are hidden.
 
+credentials
+-----------
+
+By default, all access to the upper, lower and work directories is the
+recorded mounter's MAC and DAC credentials.  The incoming accesses are
+checked against the caller's credentials.
+
+In the case where caller MAC or DAC credentials do not overlap, a
+use case available in older versions of the driver, the
+override_creds mount flag can be turned off and help when the use
+pattern has caller with legitimate credentials where the mounter
+does not.  Several unintended side effects will occur though.  The
+caller without certain key capabilities or lower privilege will not
+always be able to delete files or directories, create nodes, or
+search some restricted directories.  The ability to search and read
+a directory entry is spotty as a result of the cache mechanism not
+retesting the credentials because of the assumption, a privileged
+caller can fill cache, then a lower privilege can read the directory
+cache.  The uneven security model where cache, upperdir and workdir
+are opened at privilege, but accessed without creating a form of
+privilege escalation, should only be used with strict understanding
+of the side effects and of the security policies.
+
 whiteouts and opaque directories
 --------------------------------
 
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index b801c6353100..1c1b9415e533 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -886,7 +886,7 @@ int ovl_copy_up_flags(struct dentry *dentry, int flags)
 		dput(parent);
 		dput(next);
 	}
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 
 	return err;
 }
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 702aa63f6774..49b8ffc1294f 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -563,7 +563,8 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
 		override_cred->fsgid = inode->i_gid;
 		if (!attr->hardlink) {
 			err = security_dentry_create_files_as(dentry,
-					attr->mode, &dentry->d_name, old_cred,
+					attr->mode, &dentry->d_name,
+					old_cred ? old_cred : current_cred(),
 					override_cred);
 			if (err) {
 				put_cred(override_cred);
@@ -579,7 +580,7 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
 			err = ovl_create_over_whiteout(dentry, inode, attr);
 	}
 out_revert_creds:
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 	return err;
 }
 
@@ -655,7 +656,7 @@ static int ovl_set_link_redirect(struct dentry *dentry)
 
 	old_cred = ovl_override_creds(dentry->d_sb);
 	err = ovl_set_redirect(dentry, false);
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 
 	return err;
 }
@@ -851,7 +852,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 		err = ovl_remove_upper(dentry, is_dir, &list);
 	else
 		err = ovl_remove_and_whiteout(dentry, &list);
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 	if (!err) {
 		if (is_dir)
 			clear_nlink(dentry->d_inode);
@@ -1221,7 +1222,7 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
 out_unlock:
 	unlock_rename(new_upperdir, old_upperdir);
 out_revert_creds:
-	revert_creds(old_cred);
+	ovl_revert_creds(old->d_sb, old_cred);
 	if (update_nlink)
 		ovl_nlink_end(new);
 out_drop_write:
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index e235a635d9ec..d94d6ec785a7 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -32,7 +32,7 @@ static struct file *ovl_open_realfile(const struct file *file,
 	old_cred = ovl_override_creds(inode->i_sb);
 	realfile = open_with_fake_path(&file->f_path, flags, realinode,
 				       current_cred());
-	revert_creds(old_cred);
+	ovl_revert_creds(inode->i_sb, old_cred);
 
 	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
 		 file, file, ovl_whatisit(inode, realinode), file->f_flags,
@@ -176,7 +176,7 @@ static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
 
 	old_cred = ovl_override_creds(inode->i_sb);
 	ret = vfs_llseek(real.file, offset, whence);
-	revert_creds(old_cred);
+	ovl_revert_creds(inode->i_sb, old_cred);
 
 	file->f_pos = real.file->f_pos;
 	inode_unlock(inode);
@@ -242,7 +242,7 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
 			    ovl_iocb_to_rwf(iocb));
-	revert_creds(old_cred);
+	ovl_revert_creds(file_inode(file)->i_sb, old_cred);
 
 	ovl_file_accessed(file);
 
@@ -278,7 +278,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
 			     ovl_iocb_to_rwf(iocb));
 	file_end_write(real.file);
-	revert_creds(old_cred);
+	ovl_revert_creds(file_inode(file)->i_sb, old_cred);
 
 	/* Update size */
 	ovl_copyattr(ovl_inode_real(inode), inode);
@@ -305,7 +305,7 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
 		old_cred = ovl_override_creds(file_inode(file)->i_sb);
 		ret = vfs_fsync_range(real.file, start, end, datasync);
-		revert_creds(old_cred);
+		ovl_revert_creds(file_inode(file)->i_sb, old_cred);
 	}
 
 	fdput(real);
@@ -329,7 +329,7 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = call_mmap(vma->vm_file, vma);
-	revert_creds(old_cred);
+	ovl_revert_creds(file_inode(file)->i_sb, old_cred);
 
 	if (ret) {
 		/* Drop reference count from new vm_file value */
@@ -357,7 +357,7 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = vfs_fallocate(real.file, mode, offset, len);
-	revert_creds(old_cred);
+	ovl_revert_creds(file_inode(file)->i_sb, old_cred);
 
 	/* Update size */
 	ovl_copyattr(ovl_inode_real(inode), inode);
@@ -379,7 +379,7 @@ static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = vfs_fadvise(real.file, offset, len, advice);
-	revert_creds(old_cred);
+	ovl_revert_creds(file_inode(file)->i_sb, old_cred);
 
 	fdput(real);
 
@@ -399,7 +399,7 @@ static long ovl_real_ioctl(struct file *file, unsigned int cmd,
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = vfs_ioctl(real.file, cmd, arg);
-	revert_creds(old_cred);
+	ovl_revert_creds(file_inode(file)->i_sb, old_cred);
 
 	fdput(real);
 
@@ -589,7 +589,7 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
 						flags);
 		break;
 	}
-	revert_creds(old_cred);
+	ovl_revert_creds(file_inode(file_out)->i_sb, old_cred);
 
 	/* Update size */
 	ovl_copyattr(ovl_inode_real(inode_out), inode_out);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 1bf11ae44313..fc1828aa30ed 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -61,7 +61,7 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
 		inode_lock(upperdentry->d_inode);
 		old_cred = ovl_override_creds(dentry->d_sb);
 		err = notify_change(upperdentry, attr, NULL);
-		revert_creds(old_cred);
+		ovl_revert_creds(dentry->d_sb, old_cred);
 		if (!err)
 			ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
 		inode_unlock(upperdentry->d_inode);
@@ -257,7 +257,7 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
 		stat->nlink = dentry->d_inode->i_nlink;
 
 out:
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 
 	return err;
 }
@@ -291,7 +291,7 @@ int ovl_permission(struct inode *inode, int mask)
 		mask |= MAY_READ;
 	}
 	err = inode_permission(realinode, mask);
-	revert_creds(old_cred);
+	ovl_revert_creds(inode->i_sb, old_cred);
 
 	return err;
 }
@@ -308,7 +308,7 @@ static const char *ovl_get_link(struct dentry *dentry,
 
 	old_cred = ovl_override_creds(dentry->d_sb);
 	p = vfs_get_link(ovl_dentry_real(dentry), done);
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 	return p;
 }
 
@@ -351,7 +351,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 		WARN_ON(flags != XATTR_REPLACE);
 		err = vfs_removexattr(realdentry, name);
 	}
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 
 	/* copy c/mtime */
 	ovl_copyattr(d_inode(realdentry), inode);
@@ -373,7 +373,7 @@ int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
 	old_cred = ovl_override_creds(dentry->d_sb);
 	res = __vfs_getxattr(realdentry, d_inode(realdentry), name,
 			     value, size, flags);
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 	return res;
 }
 
@@ -397,7 +397,7 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
 
 	old_cred = ovl_override_creds(dentry->d_sb);
 	res = vfs_listxattr(realdentry, list, size);
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 	if (res <= 0 || size == 0)
 		return res;
 
@@ -432,7 +432,7 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type)
 
 	old_cred = ovl_override_creds(inode->i_sb);
 	acl = get_acl(realinode, type);
-	revert_creds(old_cred);
+	ovl_revert_creds(inode->i_sb, old_cred);
 
 	return acl;
 }
@@ -470,7 +470,7 @@ static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		filemap_write_and_wait(realinode->i_mapping);
 
 	err = realinode->i_op->fiemap(realinode, fieinfo, start, len);
-	revert_creds(old_cred);
+	ovl_revert_creds(inode->i_sb, old_cred);
 
 	return err;
 }
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index a4a452c489fa..bab1f97dc201 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -1079,7 +1079,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			goto out_free_oe;
 	}
 
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 	if (origin_path) {
 		dput(origin_path->dentry);
 		kfree(origin_path);
@@ -1106,7 +1106,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	kfree(upperredirect);
 out:
 	kfree(d.redirect);
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 	return ERR_PTR(err);
 }
 
@@ -1160,7 +1160,7 @@ bool ovl_lower_positive(struct dentry *dentry)
 			dput(this);
 		}
 	}
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 
 	return positive;
 }
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 9d26d8758513..ad1a11e7ecbd 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -205,6 +205,7 @@ int ovl_want_write(struct dentry *dentry);
 void ovl_drop_write(struct dentry *dentry);
 struct dentry *ovl_workdir(struct dentry *dentry);
 const struct cred *ovl_override_creds(struct super_block *sb);
+void ovl_revert_creds(struct super_block *sb, const struct cred *oldcred);
 ssize_t ovl_do_vfs_getxattr(struct dentry *dentry, const char *name, void *buf,
 			    size_t size);
 struct super_block *ovl_same_sb(struct super_block *sb);
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 28a2d12a1029..2637c5aadf7f 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -17,6 +17,7 @@ struct ovl_config {
 	bool nfs_export;
 	int xino;
 	bool metacopy;
+	bool override_creds;
 };
 
 struct ovl_sb {
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 47a91c9733a5..874a1b3ff99a 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -286,7 +286,7 @@ static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
 		}
 		inode_unlock(dir->d_inode);
 	}
-	revert_creds(old_cred);
+	ovl_revert_creds(rdd->dentry->d_sb, old_cred);
 
 	return err;
 }
@@ -918,7 +918,7 @@ int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
 
 	old_cred = ovl_override_creds(dentry->d_sb);
 	err = ovl_dir_read_merged(dentry, list, &root);
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 	if (err)
 		return err;
 
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 6f041e1fceda..2c1278451f38 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -53,6 +53,11 @@ module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
 MODULE_PARM_DESC(xino_auto,
 		 "Auto enable xino feature");
 
+static bool __read_mostly ovl_override_creds_def = true;
+module_param_named(override_creds, ovl_override_creds_def, bool, 0644);
+MODULE_PARM_DESC(ovl_override_creds_def,
+		 "Use mounter's credentials for accesses");
+
 static void ovl_entry_stack_free(struct ovl_entry *oe)
 {
 	unsigned int i;
@@ -362,6 +367,9 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 	if (ofs->config.metacopy != ovl_metacopy_def)
 		seq_printf(m, ",metacopy=%s",
 			   ofs->config.metacopy ? "on" : "off");
+	if (ofs->config.override_creds != ovl_override_creds_def)
+		seq_show_option(m, "override_creds",
+				ofs->config.override_creds ? "on" : "off");
 	return 0;
 }
 
@@ -402,6 +410,8 @@ enum {
 	OPT_XINO_AUTO,
 	OPT_METACOPY_ON,
 	OPT_METACOPY_OFF,
+	OPT_OVERRIDE_CREDS_ON,
+	OPT_OVERRIDE_CREDS_OFF,
 	OPT_ERR,
 };
 
@@ -420,6 +430,8 @@ static const match_table_t ovl_tokens = {
 	{OPT_XINO_AUTO,			"xino=auto"},
 	{OPT_METACOPY_ON,		"metacopy=on"},
 	{OPT_METACOPY_OFF,		"metacopy=off"},
+	{OPT_OVERRIDE_CREDS_ON,		"override_creds=on"},
+	{OPT_OVERRIDE_CREDS_OFF,	"override_creds=off"},
 	{OPT_ERR,			NULL}
 };
 
@@ -478,6 +490,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 	config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
 	if (!config->redirect_mode)
 		return -ENOMEM;
+	config->override_creds = ovl_override_creds_def;
 
 	while ((p = ovl_next_opt(&opt)) != NULL) {
 		int token;
@@ -558,6 +571,14 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 			config->metacopy = false;
 			break;
 
+		case OPT_OVERRIDE_CREDS_ON:
+			config->override_creds = true;
+			break;
+
+		case OPT_OVERRIDE_CREDS_OFF:
+			config->override_creds = false;
+			break;
+
 		default:
 			pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
 			return -EINVAL;
@@ -1674,7 +1695,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 		       ovl_dentry_lower(root_dentry), NULL);
 
 	sb->s_root = root_dentry;
-
 	return 0;
 
 out_free_oe:
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index c588c0d66d8c..9e97e785e44c 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -37,9 +37,17 @@ const struct cred *ovl_override_creds(struct super_block *sb)
 {
 	struct ovl_fs *ofs = sb->s_fs_info;
 
+	if (!ofs->config.override_creds)
+		return NULL;
 	return override_creds(ofs->creator_cred);
 }
 
+void ovl_revert_creds(struct super_block *sb, const struct cred *old_cred)
+{
+	if (old_cred)
+		revert_creds(old_cred);
+}
+
 ssize_t ovl_do_vfs_getxattr(struct dentry *dentry, const char *name, void *buf,
 			    size_t size)
 {
@@ -798,7 +806,7 @@ int ovl_nlink_start(struct dentry *dentry)
 	 * value relative to the upper inode nlink in an upper inode xattr.
 	 */
 	err = ovl_set_nlink_upper(dentry);
-	revert_creds(old_cred);
+	ovl_revert_creds(dentry->d_sb, old_cred);
 
 out:
 	if (err)
@@ -816,7 +824,7 @@ void ovl_nlink_end(struct dentry *dentry)
 
 		old_cred = ovl_override_creds(dentry->d_sb);
 		ovl_cleanup_index(dentry);
-		revert_creds(old_cred);
+		ovl_revert_creds(dentry->d_sb, old_cred);
 	}
 
 	ovl_inode_unlock(inode);
-- 
2.22.0.770.g0f2c4a37fd-goog



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^ permalink raw reply	[flat|nested] 7+ messages in thread

* [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off
  2019-07-31 16:57 [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel
                   ` (4 preceding siblings ...)
  2019-07-31 16:58 ` [f2fs-dev] [PATCH v13 5/5] overlayfs: override_creds=off option bypass creator_cred Mark Salyzyn via Linux-f2fs-devel
@ 2019-07-31 16:58 ` Mark Salyzyn via Linux-f2fs-devel
  5 siblings, 0 replies; 7+ messages in thread
From: Mark Salyzyn via Linux-f2fs-devel @ 2019-07-31 16:58 UTC (permalink / raw)
  To: linux-kernel
  Cc: Latchesar Ionkov, Dave Kleikamp, jfs-discussion, Randy Dunlap,
	linux-doc, Martin Brandenburg, samba-technical,
	Dominique Martinet, Amir Goldstein, David Howells, Chris Mason,
	David S . Miller, Andreas Dilger, ocfs2-devel, netdev,
	Tyler Hicks, linux-afs, Mike Marshall, linux-xfs,
	Andreas Gruenbacher, Sage Weil, Jonathan Corbet,
	Richard Weinberger, Mark Fasheh, devel, Hugh Dickins,
	linux-security-module, cluster-devel, Vyacheslav Dubeyko,
	v9fs-developer, Ilya Dryomov, linux-ext4, Stephen Smalley,
	linux-mm, Vivek Goyal, linux-cifs, Eric Van Hensbergen, ecryptfs,
	Josef Bacik, Darrick J . Wong, reiserfs-devel, Tejun Heo,
	Greg Kroah-Hartman, Joel Becker, linux-mtd, David Sterba,
	Jaegeuk Kim, ceph-devel, Trond Myklebust, linux-nfs,
	linux-f2fs-devel, Theodore Ts'o, linux-fsdevel, Joseph Qi,
	Mathieu Malaterre, kernel-team, Miklos Szeredi, Jeff Layton,
	linux-unionfs, stable, Mark Salyzyn, Steve French,
	Ernesto A . Fernandez, Eric W . Biederman, Jan Kara,
	Bob Peterson, Phillip Lougher, Andrew Morton, David Woodhouse,
	Anna Schumaker, linux-btrfs, Alexander Viro

Patch series:

overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh
Add flags option to get xattr method paired to __vfs_getxattr
overlayfs: handle XATTR_NOSECURITY flag for get xattr method
overlayfs: internal getxattr operations without sepolicy checking
overlayfs: override_creds=off option bypass creator_cred

The first four patches address fundamental security issues that should
be solved regardless of the override_creds=off feature.
on them).

The fifth adds the feature depends on these other fixes.

By default, all access to the upper, lower and work directories is the
recorded mounter's MAC and DAC credentials.  The incoming accesses are
checked against the caller's credentials.

If the principles of least privilege are applied for sepolicy, the
mounter's credentials might not overlap the credentials of the caller's
when accessing the overlayfs filesystem.  For example, a file that a
lower DAC privileged caller can execute, is MAC denied to the
generally higher DAC privileged mounter, to prevent an attack vector.

We add the option to turn off override_creds in the mount options; all
subsequent operations after mount on the filesystem will be only the
caller's credentials.  The module boolean parameter and mount option
override_creds is also added as a presence check for this "feature",
existence of /sys/module/overlay/parameters/overlay_creds

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: linux-unionfs@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Steve French <sfrench@samba.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Jan Kara <jack@suse.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mike Marshall <hubcap@omnibond.com>
Cc: Martin Brandenburg <martin@omnibond.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Cc: Hugh Dickins <hughd@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Ernesto A. Fernandez <ernesto.mnd.fernandez@gmail.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: v9fs-developer@lists.sourceforge.net
Cc: linux-afs@lists.infradead.org
Cc: linux-btrfs@vger.kernel.org
Cc: ceph-devel@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: ecryptfs@vger.kernel.org
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: linux-fsdevel@vger.kernel.org
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: devel@lists.orangefs.org
Cc: reiserfs-devel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: netdev@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: stable@vger.kernel.org # 4.4, 4.9, 4.14 & 4.19
---
v13:
- add flags argument to __vfs_getxattr
- drop GFP_NOFS side-effect

v12:
- Restore squished out patch 2 and 3 in the series,
  then change algorithm to add flags argument.
  Per-thread flag is a large security surface.

v11:
- Squish out v10 introduced patch 2 and 3 in the series,
  then and use per-thread flag instead for nesting.
- Switch name to ovl_do_vds_getxattr for __vds_getxattr wrapper.
- Add sb argument to ovl_revert_creds to match future work.

v10:
- Return NULL on CAP_DAC_READ_SEARCH
- Add __get xattr method to solve sepolicy logging issue
- Drop unnecessary sys_admin sepolicy checking for administrative
  driver internal xattr functions.

v6:
- Drop CONFIG_OVERLAY_FS_OVERRIDE_CREDS.
- Do better with the documentation, drop rationalizations.
- pr_warn message adjusted to report consequences.

v5:
- beefed up the caveats in the Documentation
- Is dependent on
  "overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh"
  "overlayfs: check CAP_MKNOD before issuing vfs_whiteout"
- Added prwarn when override_creds=off

v4:
- spelling and grammar errors in text

v3:
- Change name from caller_credentials / creator_credentials to the
  boolean override_creds.
- Changed from creator to mounter credentials.
- Updated and fortified the documentation.
- Added CONFIG_OVERLAY_FS_OVERRIDE_CREDS

v2:
- Forward port changed attr to stat, resulting in a build error.
- altered commit message.


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^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, back to index

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-31 16:57 [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel
2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 1/5] overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh Mark Salyzyn via Linux-f2fs-devel
2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 2/5] Add flags option to get xattr method paired to __vfs_getxattr Mark Salyzyn via Linux-f2fs-devel
2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 3/5] overlayfs: handle XATTR_NOSECURITY flag for get xattr method Mark Salyzyn via Linux-f2fs-devel
2019-07-31 16:57 ` [f2fs-dev] [PATCH v13 4/5] overlayfs: internal getxattr operations without sepolicy checking Mark Salyzyn via Linux-f2fs-devel
2019-07-31 16:58 ` [f2fs-dev] [PATCH v13 5/5] overlayfs: override_creds=off option bypass creator_cred Mark Salyzyn via Linux-f2fs-devel
2019-07-31 16:58 ` [f2fs-dev] [PATCH v13 0/5] overlayfs override_creds=off Mark Salyzyn via Linux-f2fs-devel

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