파일을 읽을 수 있는 권한이 있는 이유를 어떻게 알 수 있나요? [폐쇄]

CentOS SSH 계정에서 방금 확인한 내용은 다음과 같습니다.

통계 출력

$ stat /dev/kvm   
  File: `/dev/kvm'
  Size: 0               Blocks: 0          IO Block: 4096   character special file
Device: 5h/5d   Inode: 39768216    Links: 1     Device type: a,e8
Access: (0666/crw-rw-rw-)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2014-07-12 13:50:33.015216048 +0200
Modify: 2014-07-12 13:50:33.015216048 +0200
Change: 2014-07-12 13:50:33.015216048 +0200

신원 정보

$ id
uid=502(jacek) gid=502(jacek) groups=502(jacek)

추적 출력

$ strace -e open cat /dev/kvm
open("/etc/ld.so.cache", O_RDONLY)      = 3
open("/lib64/libc.so.6", O_RDONLY)      = 3
open("/usr/lib/locale/locale-archive", O_RDONLY) = 3
open("/dev/kvm", O_RDONLY)              = 3
cat: /dev/kvmopen("/usr/share/locale/locale.alias", O_RDONLY) = 4
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
: Invalid argument

액세스 제어 목록 정보

$ getfacl /dev/kvm
getfacl: Removing leading '/' from absolute path names
# file: dev/kvm
# owner: root
# group: root
user::rw-
group::rw-
other::rw-

여기서 왜 open성공했나요? ACL 외에도 사용자가 파일을 열 수 있는지 여부를 결정하는 데 사용할 수 있는 메커니즘이 있습니까? 쿼리하려면 어떤 명령을 사용할 수 있나요?