commit 073931017b upstream.
When file permissions are modified via chmod(2) and the user is not in
the owning group or capable of CAP_FSETID, the setgid bit is cleared in
inode_change_ok(). Setting a POSIX ACL via setxattr(2) sets the file
permissions as well as the new ACL, but doesn't clear the setgid bit in
a similar way; this allows to bypass the check in chmod(2). Fix that.
References: CVE-2016-7097
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
[bwh: Backported to 3.2:
- Drop changes to ceph, f2fs, hfsplus, orangefs
- Use capable() instead of capable_wrt_inode_uidgid()
- Update ext3 and generic_acl.c as well
- In gfs2, jfs, and xfs, take care to avoid leaking the allocated ACL if
posix_acl_update_mode() determines it's not needed
- Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
a06d3be52b