Samba

沒有 EOF，當程序在 cifs mount 上讀取自己的執行檔時

  • July 22, 2017

我的基於 java 的安裝程序無法將自身複製到目標目錄，吃掉所有磁碟空間，我認為這是一個 java 錯誤，但後來我用 plain 複製了它dd。

當我嘗試使用足夠大的緩衝區（131072）讀取我自己的執行檔時，讀取操作突然返回大於實際文件大小的值並且永遠不會返回 EOF：

DD=/media/distr/dd
(
/bin/cp /bin/dd $DD
$DD bs=131071 if=$DD of=/dev/null count=20
$DD bs=131072 if=$DD of=/dev/null count=20
)
0+1 records in
0+1 records out
55256 bytes (55 kB) copied, 0.00211071 s, 26.2 MB/s
20+0 records in
20+0 records out
2621440 bytes (2.6 MB) copied, 0.0194318 s, 135 MB/s

僅當samba伺服器和cifs掛載都在 Oracle Linux 6.6 上執行時才會發生samba 3.6.23-12.0.1.el6。

它是什麼？核心、cifs 或 samba 錯誤？

dd的strace：

[root@ec-stage-db-2 ~]# strace $DD bs=131072 if=$DD of=/dev/null count=20
execve("/mnt/dd", ["/mnt/dd", "bs=131072", "if=/mnt/dd", "of=/dev/null", "count=20"], [/* 32 vars */]) = 0
brk(0)                                  = 0x13e8000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fcc172ee000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=79239, ...}) = 0
mmap(NULL, 79239, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fcc172da000
close(3)                                = 0
open("/lib64/librt.so.1", O_RDONLY)     = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0@!\3002=\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=47104, ...}) = 0
mmap(0x3d32c00000, 2128816, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x3d32c00000
mprotect(0x3d32c07000, 2093056, PROT_NONE) = 0
mmap(0x3d32e06000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6000) = 0x3d32e06000
close(3)                                = 0
open("/lib64/libc.so.6", O_RDONLY)      = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0p\356\3011=\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1926760, ...}) = 0
mmap(0x3d31c00000, 3750152, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x3d31c00000
mprotect(0x3d31d8a000, 2097152, PROT_NONE) = 0
mmap(0x3d31f8a000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x18a000) = 0x3d31f8a000
mmap(0x3d31f8f000, 18696, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x3d31f8f000
close(3)                                = 0
open("/lib64/libpthread.so.0", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\340]\0002=\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=145896, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fcc172d9000
mmap(0x3d32000000, 2212848, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x3d32000000
mprotect(0x3d32017000, 2097152, PROT_NONE) = 0
mmap(0x3d32217000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x17000) = 0x3d32217000
mmap(0x3d32219000, 13296, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x3d32219000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fcc172d8000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fcc172d7000
arch_prctl(ARCH_SET_FS, 0x7fcc172d8700) = 0
mprotect(0x3d32e06000, 4096, PROT_READ) = 0
mprotect(0x3d31f8a000, 16384, PROT_READ) = 0
mprotect(0x3d32217000, 4096, PROT_READ) = 0
mprotect(0x3d3161f000, 4096, PROT_READ) = 0
munmap(0x7fcc172da000, 79239)           = 0
set_tid_address(0x7fcc172d89d0)         = 39608
set_robust_list(0x7fcc172d89e0, 0x18)   = 0
futex(0x7fffa32a778c, FUTEX_WAKE_PRIVATE, 1) = 0
futex(0x7fffa32a778c, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 1, NULL, 7fcc172d8700) = -1 EAGAIN (Resource temporarily unavailable)
rt_sigaction(SIGRTMIN, {0x3d32005c60, [], SA_RESTORER|SA_SIGINFO, 0x3d3200f710}, NULL, 8) = 0
rt_sigaction(SIGRT_1, {0x3d32005cf0, [], SA_RESTORER|SA_RESTART|SA_SIGINFO, 0x3d3200f710}, NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
getrlimit(RLIMIT_STACK, {rlim_cur=8192*1024, rlim_max=RLIM_INFINITY}) = 0
rt_sigaction(SIGUSR1, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGINT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGUSR1, {0x401be0, [INT USR1], SA_RESTORER, 0x3d31c326a0}, NULL, 8) = 0
rt_sigaction(SIGINT, {0x401bd0, [INT USR1], SA_RESTORER|SA_NODEFER|SA_RESETHAND, 0x3d31c326a0}, NULL, 8) = 0
brk(0)                                  = 0x13e8000
brk(0x1409000)                          = 0x1409000
open("/usr/lib/locale/locale-archive", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=99158576, ...}) = 0
mmap(NULL, 99158576, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fcc11446000
close(3)                                = 0
open("/mnt/dd", O_RDONLY)               = 3
dup2(3, 0)                              = 0
close(3)                                = 0
lseek(0, 0, SEEK_CUR)                   = 0
open("/dev/null", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
dup2(3, 1)                              = 1
close(3)                                = 0
mmap(NULL, 143360, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fcc11423000
read(0, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\2\0>\0\1\0\0\0\340\32@\0\0\0\0\0"..., 131072) = 131072
write(1, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\2\0>\0\1\0\0\0\340\32@\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072
close(0)                                = 0
close(1)                                = 0
open("/usr/share/locale/locale.alias", O_RDONLY) = 0
fstat(0, {st_mode=S_IFREG|0644, st_size=2512, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fcc172ed000
read(0, "# Locale name alias data base.\n#"..., 4096) = 2512
read(0, "", 4096)                       = 0
close(0)                                = 0
munmap(0x7fcc172ed000, 4096)            = 0
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = 0
fstat(0, {st_mode=S_IFREG|0644, st_size=435, ...}) = 0
mmap(NULL, 435, PROT_READ, MAP_PRIVATE, 0, 0) = 0x7fcc172ed000
close(0)                                = 0
write(2, "20+0 records in\n20+0 records out"..., 3320+0 records in
20+0 records out
) = 33
write(2, "2621440 bytes (2.6 MB) copied", 292621440 bytes (2.6 MB) copied) = 29
write(2, ", 0.0245485 s, 107 MB/s\n", 24, 0.0245485 s, 107 MB/s
) = 24
close(2)                                = 0
exit_group(0)                           = ?

完成測試腳本。我不能報告這個錯誤，因為我必須為此付費。

#!/bin/bash

set -e

# systemd
#SMB_START="systemctl start smbd.service nmbd.service"
#SMB_RELOAD="systemctl reload smbd.service"

# initscripts
SMB_START="service smb start"
SMB_RELOAD="service smb reload"

cleanup() {
echo cleanup... >&2
sed -i -n -e "/# added by test-samba-bug BEGIN/b m10; p; b" -e :m10 -e n -e "/# added by test-samba-bug END/b" -e "b m10" /etc/samba/smb.conf
umount -f /tmp/test-samba-bug-mnt 2>/dev/null || true
rm -rf /tmp/test-samba-bug /tmp/test-samba-bug-mnt
}

cleanup

trap cleanup EXIT

mkdir -p /tmp/test-samba-bug /tmp/test-samba-bug-mnt
chcon -R -t samba_share_t /tmp/test-samba-bug 2>/dev/null || true

>>/etc/samba/smb.conf cat <<EOF
# added by test-samba-bug BEGIN
[test-samba-bug]
       path = /tmp/test-samba-bug
       public = yes
# added by test-samba-bug END
EOF

# service smb stop
$SMB_START
$SMB_RELOAD

mount -t cifs -oguest //localhost/test-samba-bug /tmp/test-samba-bug-mnt

command cp /bin/dd /tmp/test-samba-bug/

DD=/tmp/test-samba-bug-mnt/dd

#$DD bs=131071 if=$DD of=/dev/null count=20
$DD bs=131072 if=$DD of=/tmp/test-samba-bug/copied count=20

echo comparing copied file contents
cmp /bin/dd /tmp/test-samba-bug/copied || {
echo "test failed" >&2
exit 1
}

假設你不能在同一台機器上用另一個文件系統重現這個問題，它一定是一個 samba 錯誤。

無論是客戶端還是伺服器問題都有點爭議，但我猜這與映射執行並打開讀取的同一個文件有關，這可能處理不正確，因為讀取呼叫不應該返回任何超出eof的東西。錯誤的文件元數據（即大小）也可能導致此類行為。

引用自：https://unix.stackexchange.com/questions/168861

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