[RESEND PATCH v18 0/4] overlayfs override_creds=off & nested get xattr fix
Mark Salyzyn
salyzyn at android.com
Wed Oct 21 15:18:59 UTC 2020
Mark Salyzyn (3):
Add flags option to get xattr method paired to __vfs_getxattr
overlayfs: handle XATTR_NOSECURITY flag for get xattr method
overlayfs: override_creds=off option bypass creator_cred
Mark Salyzyn + John Stultz (1):
overlayfs: inode_owner_or_capable called during execv
The first three patches address fundamental security issues that should
be solved regardless of the override_creds=off feature.
The fourth 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 at android.com>
Cc: Miklos Szeredi <miklos at szeredi.hu>
Cc: Jonathan Corbet <corbet at lwn.net>
Cc: Vivek Goyal <vgoyal at redhat.com>
Cc: Eric W. Biederman <ebiederm at xmission.com>
Cc: Amir Goldstein <amir73il at gmail.com>
Cc: Randy Dunlap <rdunlap at infradead.org>
Cc: Stephen Smalley <sds at tycho.nsa.gov>
Cc: John Stultz <john.stultz at linaro.org>
Cc: linux-doc at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Cc: linux-fsdevel at vger.kernel.org
Cc: linux-unionfs at vger.kernel.org
Cc: linux-security-module at vger.kernel.org
Cc: kernel-team at android.com
Cc: selinux at vger.kernel.org
---
v18
- rebase + fix minor cut and paste error for inode argument in __vfs_getxattr
v17
- correct some zero-day build failures.
- fix up documentation
v16
- rebase and merge of two patches.
- add adjustment to deal with execv when overrides is off.
v15
- Revert back to v4 with fixes from on the way from v5-v14. The single
structure argument passing to address the complaints about too many
arguments was rejected by the community.
- Drop the udner discussion fix for an additional CAP_DAC_READ_SEARCH
check. Can address that independently.
- ToDo: upstream test frame for thes security fixes (currently testing
is all in Android).
v14:
- Rejoin, rebase and a few adjustments.
v13:
- Pull out first patch and try to get it in alone feedback, some
Acks, and then <crickets> because people forgot why we were doing i.
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.
Documentation/filesystems/locking.rst | 2 +-
Documentation/filesystems/overlayfs.rst | 26 +++++++++++++++++-
fs/9p/acl.c | 3 ++-
fs/9p/xattr.c | 3 ++-
fs/afs/xattr.c | 10 +++----
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/erofs/xattr.c | 3 ++-
fs/ext2/xattr_security.c | 2 +-
fs/ext2/xattr_trusted.c | 2 +-
fs/ext2/xattr_user.c | 2 +-
fs/ext4/xattr_hurd.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_security.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 | 9 ++++---
fs/ocfs2/xattr.c | 9 ++++---
fs/orangefs/xattr.c | 3 ++-
fs/overlayfs/copy_up.c | 2 +-
fs/overlayfs/dir.c | 17 +++++++-----
fs/overlayfs/file.c | 26 +++++++++---------
fs/overlayfs/inode.c | 23 ++++++++--------
fs/overlayfs/namei.c | 6 ++---
fs/overlayfs/overlayfs.h | 7 +++--
fs/overlayfs/ovl_entry.h | 1 +
fs/overlayfs/readdir.c | 8 +++---
fs/overlayfs/super.c | 34 ++++++++++++++++++-----
fs/overlayfs/util.c | 13 +++++++--
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/ubifs/xattr.c | 3 ++-
fs/xattr.c | 36 ++++++++++++-------------
fs/xfs/xfs_xattr.c | 3 ++-
include/linux/xattr.h | 9 ++++---
include/uapi/linux/xattr.h | 7 +++--
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 ++--
60 files changed, 242 insertions(+), 137 deletions(-)
--
2.29.0.rc1.297.gfa9743e501-goog
More information about the Linux-security-module-archive
mailing list