背景

今天学弟在使用 NVMe-over-TCP 时发现无法卸载 nvmet 驱动，显示使用中

在一起探讨和测试中发现最终的原因竟然在于 rm -r 和 rmdir 这两个命令上

二者区别

命令 主要系统调用 操作对象
rmdir rmdir 仅目录
rm -r openat, getdents64, close, unlinkat 目录，以及目录所有文件

rmdir

rmdir 直接调用 rmdir 来删除目录，如果目录非空，则会删除失败

rm -r

  1. 会先用 openat 打开目录，通过 getdents64 获取目录中的内容，然后 close 目录
  2. 再第二次加上 O_CLOEXEC 标记openat 打开目录，表明当前目录即将删除，再次通过 getdents64 获取目录中的内容，然后 close 目录
  3. 然后依次通过 unlinkat 删除目录中的内容
  4. 最后通过 unlinkat 删除目录

rm -rf

但是如果使用的是 rm -rf，并且在第 3 步删除目录内文件失败时，则会跳过第 4 步，也就是说不会再对目录做任何操作

测试过程

配置环境

首先建立一个非空目录，并且给目录中的文件配置权限，禁止删除文件

mkdir dir

touch dir/file

sudo chattr +i dir/file

此时目录树如下

$ tree dir

dir

└── file

0 directories, 1 file

rmdir

$ strace -o rmdir rmdir dir/

rmdir: failed to remove 'dir/': Directory not empty

strace 抓到的内容如下，主要内容在第 37 行

execve("/usr/bin/rmdir", ["rmdir", "dir/"], 0x7ffe38ddae38 /* 26 vars */) = 0

brk(NULL)                               = 0x561e92b83000

arch_prctl(0x3001 /* ARCH_??? */, 0x7fff06684960) = -1 EINVAL (Invalid argument)

access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=46019, ...}) = 0

mmap(NULL, 46019, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f51af80c000

close(3)                                = 0

openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3

read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360q\2\0\0\0\0\0"..., 832) = 832

pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784

pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32

pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\t\233\222%\274\260\320\31\331\326\10\204\276X>\263"..., 68, 880) = 68

fstat(3, {st_mode=S_IFREG|0755, st_size=2029224, ...}) = 0

mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f51af80a000

pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784

pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32

pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\t\233\222%\274\260\320\31\331\326\10\204\276X>\263"..., 68, 880) = 68

mmap(NULL, 2036952, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f51af618000

mprotect(0x7f51af63d000, 1847296, PROT_NONE) = 0

mmap(0x7f51af63d000, 1540096, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x25000) = 0x7f51af63d000

mmap(0x7f51af7b5000, 303104, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19d000) = 0x7f51af7b5000

mmap(0x7f51af800000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f51af800000

mmap(0x7f51af806000, 13528, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f51af806000

close(3)                                = 0

arch_prctl(ARCH_SET_FS, 0x7f51af80b580) = 0

mprotect(0x7f51af800000, 12288, PROT_READ) = 0

mprotect(0x561e91688000, 4096, PROT_READ) = 0

mprotect(0x7f51af845000, 4096, PROT_READ) = 0

munmap(0x7f51af80c000, 46019)           = 0

brk(NULL)                               = 0x561e92b83000

brk(0x561e92ba4000)                     = 0x561e92ba4000

openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=3035952, ...}) = 0

mmap(NULL, 3035952, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f51af332000

close(3)                                = 0

rmdir("dir/")                           = -1 ENOTEMPTY (Directory not empty)

openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=2996, ...}) = 0

read(3, "# Locale name alias data base.\n#"..., 4096) = 2996

read(3, "", 4096)                       = 0

close(3)                                = 0

openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

write(2, "rmdir: ", 7)                  = 7

write(2, "failed to remove 'dir/'", 23) = 23

openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

write(2, ": Directory not empty", 21)   = 21

write(2, "\n", 1)                       = 1

close(1)                                = 0

close(2)                                = 0

exit_group(1)                           = ?

+++ exited with 1 +++

rm -r

$ strace -o rm_r_fail.strace rm -r dir/

rm: cannot remove 'dir/file': Operation not permitted

rm: cannot remove 'dir/': Directory not empty

strace 抓到的内容如下，主要内容在第 39-59 以及 94-96 行

execve("/usr/bin/rm", ["rm", "-r", "dir/"], 0x7ffc2c0fb640 /* 26 vars */) = 0

brk(NULL)                               = 0x56082871e000

arch_prctl(0x3001 /* ARCH_??? */, 0x7ffd0d910cf0) = -1 EINVAL (Invalid argument)

access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=46019, ...}) = 0

mmap(NULL, 46019, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f65c441d000

close(3)                                = 0

openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3

read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360q\2\0\0\0\0\0"..., 832) = 832

pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784

pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32

pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\t\233\222%\274\260\320\31\331\326\10\204\276X>\263"..., 68, 880) = 68

fstat(3, {st_mode=S_IFREG|0755, st_size=2029224, ...}) = 0

mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f65c441b000

pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784

pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32

pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\t\233\222%\274\260\320\31\331\326\10\204\276X>\263"..., 68, 880) = 68

mmap(NULL, 2036952, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f65c4229000

mprotect(0x7f65c424e000, 1847296, PROT_NONE) = 0

mmap(0x7f65c424e000, 1540096, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x25000) = 0x7f65c424e000

mmap(0x7f65c43c6000, 303104, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19d000) = 0x7f65c43c6000

mmap(0x7f65c4411000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f65c4411000

mmap(0x7f65c4417000, 13528, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f65c4417000

close(3)                                = 0

arch_prctl(ARCH_SET_FS, 0x7f65c441c580) = 0

mprotect(0x7f65c4411000, 12288, PROT_READ) = 0

mprotect(0x560827bb0000, 4096, PROT_READ) = 0

mprotect(0x7f65c4456000, 4096, PROT_READ) = 0

munmap(0x7f65c441d000, 46019)           = 0

brk(NULL)                               = 0x56082871e000

brk(0x56082873f000)                     = 0x56082873f000

openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=3035952, ...}) = 0

mmap(NULL, 3035952, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f65c3f43000

close(3)                                = 0

ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0

lstat("/", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0

newfstatat(AT_FDCWD, "dir/", {st_mode=S_IFDIR|0775, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0

openat(AT_FDCWD, "dir/", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_NOFOLLOW|O_DIRECTORY) = 3

fstat(3, {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0

fcntl(3, F_GETFL)                       = 0x38800 (flags O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_NOFOLLOW|O_DIRECTORY)

fcntl(3, F_SETFD, FD_CLOEXEC)           = 0

getdents64(3, /* 3 entries */, 32768)   = 72

close(3)                                = 0

geteuid()                               = 1000

newfstatat(AT_FDCWD, "dir/", {st_mode=S_IFDIR|0775, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0

faccessat(AT_FDCWD, "dir/", W_OK)       = 0

openat(AT_FDCWD, "dir/", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_NOFOLLOW|O_CLOEXEC|O_DIRECTORY) = 3

fstat(3, {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0

fcntl(3, F_GETFL)                       = 0x38800 (flags O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_NOFOLLOW|O_DIRECTORY)

fcntl(3, F_SETFD, FD_CLOEXEC)           = 0

fstatfs(3, {f_type=EXT2_SUPER_MAGIC, f_bsize=4096, f_blocks=20510566, f_bfree=15993067, f_bavail=14940434, f_files=5242880, f_ffree=5074130, f_fsid={val=[3258576323, 2412010735]}, f_namelen=255, f_frsize=4096, f_flags=ST_VALID|ST_RELATIME}) = 0

fcntl(3, F_DUPFD_CLOEXEC, 3)            = 4

getdents64(3, /* 3 entries */, 32768)   = 72

getdents64(3, /* 0 entries */, 32768)   = 0

close(3)                                = 0

newfstatat(4, "file", {st_mode=S_IFREG|0664, st_size=0, ...}, AT_SYMLINK_NOFOLLOW) = 0

faccessat(4, "file", W_OK)              = -1 EPERM (Operation not permitted)

openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=2996, ...}) = 0

read(3, "# Locale name alias data base.\n#"..., 4096) = 2996

read(3, "", 4096)                       = 0

close(3)                                = 0

openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

write(2, "rm: ", 4)                     = 4

write(2, "cannot remove 'dir/file'", 24) = 24

openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

write(2, ": Operation not permitted", 25) = 25

write(2, "\n", 1)                       = 1

close(4)                                = 0

newfstatat(AT_FDCWD, "dir/", {st_mode=S_IFDIR|0775, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0

faccessat(AT_FDCWD, "dir/", W_OK)       = 0

unlinkat(AT_FDCWD, "dir/", AT_REMOVEDIR) = -1 ENOTEMPTY (Directory not empty)

write(2, "rm: ", 4)                     = 4

write(2, "cannot remove 'dir/'", 20)    = 20

write(2, ": Directory not empty", 21)   = 21

write(2, "\n", 1)                       = 1

lseek(0, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)

close(0)                                = 0

close(1)                                = 0

close(2)                                = 0

exit_group(1)                           = ?

+++ exited with 1 +++

rm -rf

$ strace -o rm_fail.strace rm -rf dir/

rm: cannot remove 'dir/file': Operation not permitted

strace 抓到的内容如下，主要内容在第 39-55 行

execve("/usr/bin/rm", ["rm", "-rf", "dir/"], 0x7fff7bc99c20 /* 26 vars */) = 0

brk(NULL)                               = 0x5566570fe000

arch_prctl(0x3001 /* ARCH_??? */, 0x7ffde2720670) = -1 EINVAL (Invalid argument)

access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=46019, ...}) = 0

mmap(NULL, 46019, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fcb89d87000

close(3)                                = 0

openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3

read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360q\2\0\0\0\0\0"..., 832) = 832

pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784

pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32

pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\t\233\222%\274\260\320\31\331\326\10\204\276X>\263"..., 68, 880) = 68

fstat(3, {st_mode=S_IFREG|0755, st_size=2029224, ...}) = 0

mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fcb89d85000

pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784

pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32

pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\t\233\222%\274\260\320\31\331\326\10\204\276X>\263"..., 68, 880) = 68

mmap(NULL, 2036952, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fcb89b93000

mprotect(0x7fcb89bb8000, 1847296, PROT_NONE) = 0

mmap(0x7fcb89bb8000, 1540096, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x25000) = 0x7fcb89bb8000

mmap(0x7fcb89d30000, 303104, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19d000) = 0x7fcb89d30000

mmap(0x7fcb89d7b000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7fcb89d7b000

mmap(0x7fcb89d81000, 13528, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fcb89d81000

close(3)                                = 0

arch_prctl(ARCH_SET_FS, 0x7fcb89d86580) = 0

mprotect(0x7fcb89d7b000, 12288, PROT_READ) = 0

mprotect(0x5566566dd000, 4096, PROT_READ) = 0

mprotect(0x7fcb89dc0000, 4096, PROT_READ) = 0

munmap(0x7fcb89d87000, 46019)           = 0

brk(NULL)                               = 0x5566570fe000

brk(0x55665711f000)                     = 0x55665711f000

openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=3035952, ...}) = 0

mmap(NULL, 3035952, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fcb898ad000

close(3)                                = 0

ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0

lstat("/", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0

newfstatat(AT_FDCWD, "dir/", {st_mode=S_IFDIR|0775, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0

openat(AT_FDCWD, "dir/", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_NOFOLLOW|O_DIRECTORY) = 3

fstat(3, {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0

fcntl(3, F_GETFL)                       = 0x38800 (flags O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_NOFOLLOW|O_DIRECTORY)

fcntl(3, F_SETFD, FD_CLOEXEC)           = 0

getdents64(3, /* 3 entries */, 32768)   = 72

close(3)                                = 0

openat(AT_FDCWD, "dir/", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_NOFOLLOW|O_CLOEXEC|O_DIRECTORY) = 3

fstat(3, {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0

fcntl(3, F_GETFL)                       = 0x38800 (flags O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_NOFOLLOW|O_DIRECTORY)

fcntl(3, F_SETFD, FD_CLOEXEC)           = 0

fstatfs(3, {f_type=EXT2_SUPER_MAGIC, f_bsize=4096, f_blocks=20510566, f_bfree=15993067, f_bavail=14940434, f_files=5242880, f_ffree=5074130, f_fsid={val=[3258576323, 2412010735]}, f_namelen=255, f_frsize=4096, f_flags=ST_VALID|ST_RELATIME}) = 0

fcntl(3, F_DUPFD_CLOEXEC, 3)            = 4

getdents64(3, /* 3 entries */, 32768)   = 72

getdents64(3, /* 0 entries */, 32768)   = 0

close(3)                                = 0

unlinkat(4, "file", 0)                  = -1 EPERM (Operation not permitted)

openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=2996, ...}) = 0

read(3, "# Locale name alias data base.\n#"..., 4096) = 2996

read(3, "", 4096)                       = 0

close(3)                                = 0

openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

write(2, "rm: ", 4)                     = 4

write(2, "cannot remove 'dir/file'", 24) = 24

openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/usr/share/locale-langpack/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)

write(2, ": Operation not permitted", 25) = 25

write(2, "\n", 1)                       = 1

close(4)                                = 0

lseek(0, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)

close(0)                                = 0

close(1)                                = 0

close(2)                                = 0

exit_group(1)                           = ?

+++ exited with 1 +++

最后取消文件的权限，看一下 rm -rf 成功时的系统调用

sudo chattr -i dir/file

strace -o rm_rf_succ.strace rm -rf dir/

strace 抓到的内容如下，主要内容在第 39-57 行

execve("/usr/bin/rm", ["rm", "-rf", "dir/"], 0x7ffee56569a0 /* 26 vars */) = 0

brk(NULL)                               = 0x55cc9fc1d000

arch_prctl(0x3001 /* ARCH_??? */, 0x7ffec41c6210) = -1 EINVAL (Invalid argument)

access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)

openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=46019, ...}) = 0

mmap(NULL, 46019, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f771df9d000

close(3)                                = 0

openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3

read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360q\2\0\0\0\0\0"..., 832) = 832

pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784

pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32

pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\t\233\222%\274\260\320\31\331\326\10\204\276X>\263"..., 68, 880) = 68

fstat(3, {st_mode=S_IFREG|0755, st_size=2029224, ...}) = 0

mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f771df9b000

pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784

pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32

pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\t\233\222%\274\260\320\31\331\326\10\204\276X>\263"..., 68, 880) = 68

mmap(NULL, 2036952, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f771dda9000

mprotect(0x7f771ddce000, 1847296, PROT_NONE) = 0

mmap(0x7f771ddce000, 1540096, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x25000) = 0x7f771ddce000

mmap(0x7f771df46000, 303104, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19d000) = 0x7f771df46000

mmap(0x7f771df91000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f771df91000

mmap(0x7f771df97000, 13528, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f771df97000

close(3)                                = 0

arch_prctl(ARCH_SET_FS, 0x7f771df9c580) = 0

mprotect(0x7f771df91000, 12288, PROT_READ) = 0

mprotect(0x55cc9ec06000, 4096, PROT_READ) = 0

mprotect(0x7f771dfd6000, 4096, PROT_READ) = 0

munmap(0x7f771df9d000, 46019)           = 0

brk(NULL)                               = 0x55cc9fc1d000

brk(0x55cc9fc3e000)                     = 0x55cc9fc3e000

openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3

fstat(3, {st_mode=S_IFREG|0644, st_size=3035952, ...}) = 0

mmap(NULL, 3035952, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f771dac3000

close(3)                                = 0

ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0

lstat("/", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0

newfstatat(AT_FDCWD, "dir/", {st_mode=S_IFDIR|0775, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0

openat(AT_FDCWD, "dir/", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_NOFOLLOW|O_DIRECTORY) = 3

fstat(3, {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0

fcntl(3, F_GETFL)                       = 0x38800 (flags O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_NOFOLLOW|O_DIRECTORY)

fcntl(3, F_SETFD, FD_CLOEXEC)           = 0

getdents64(3, /* 3 entries */, 32768)   = 72

close(3)                                = 0

openat(AT_FDCWD, "dir/", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_NOFOLLOW|O_CLOEXEC|O_DIRECTORY) = 3

fstat(3, {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0

fcntl(3, F_GETFL)                       = 0x38800 (flags O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_NOFOLLOW|O_DIRECTORY)

fcntl(3, F_SETFD, FD_CLOEXEC)           = 0

fstatfs(3, {f_type=EXT2_SUPER_MAGIC, f_bsize=4096, f_blocks=20510566, f_bfree=15993064, f_bavail=14940431, f_files=5242880, f_ffree=5074129, f_fsid={val=[3258576323, 2412010735]}, f_namelen=255, f_frsize=4096, f_flags=ST_VALID|ST_RELATIME}) = 0

fcntl(3, F_DUPFD_CLOEXEC, 3)            = 4

getdents64(3, /* 3 entries */, 32768)   = 72

getdents64(3, /* 0 entries */, 32768)   = 0

close(3)                                = 0

unlinkat(4, "file", 0)                  = 0

close(4)                                = 0

unlinkat(AT_FDCWD, "dir/", AT_REMOVEDIR) = 0

lseek(0, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)

close(0)                                = 0

close(1)                                = 0

close(2)                                = 0

exit_group(0)                           = ?

+++ exited with 0 +++

参考资料

本文作者： ywang_wnlo

本文链接： https://ywang-wnlo.github.io/posts/935ae1f0.html

版权声明： 本博客所有文章除特别声明外，均采用 BY-NC-SA 许可协议。转载请注明出处！

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