Set CLOEXEC on the listen socket when forking FPM children

[mikhainin]

It doesn't look like a good idea to invoke fork() from the FPM worker but sometimes people may do this. If this happens, the socket may leak into the new process and break something.

The socket still can be accessed via fopren('php://fd/<FD>') but not sure if we can/should do anything about that

[mikhainin]

Basically, that was a real issue in our project.

Not sure if introducing the new function is a good idea - I will be happy to move it somewhere. It is probably worth adding a test. Let me know if you have any idea how

[bukka]

This is a known issue and there are some related reports / discussion about this:

• https://bugs.php.net/bug.php?id=67383 - exec() leaks file and socket descriptors to called program (general for all parts of PHP - not good idea)
• https://bugs.php.net/bug.php?id=76067 - system() function call leaks php-fpm listening sockets
• https://bugs.php.net/bug.php?id=80992 - fork() don't close fpm_globals.listening_socket

From re-reading the discussions I was a bit worried about stdin but not really sure why. It would be definitely good to test if it is possible to currently read from stdin in some useful way in the execed script.

Some of the reports also contained some script that could be used for the test so take a look. It would be good to have some sort of test even if it was just Linux specific.

[bukka]

NIT: we no longer use {{{ and }}} for new functions so please remove it.

[mikhainin]

Sure, I removed {{{ and will look into implementing tests.

[mikhainin]

It actually looks like the stdin is already set to /dev/null

I feel like it happens in the fpm_stdio_init_main()

Master process:

lsof -P | fgrep -w 77376
php-fpm   77376 mikhailgalanin  cwd       DIR               1,18        2080             3682735 /Users/mikhailgalanin/src/php-src
php-fpm   77376 mikhailgalanin  txt       REG               1,18    50481108           227463483 /Users/mikhailgalanin/src/php-src/sapi/fpm/php-fpm
php-fpm   77376 mikhailgalanin  txt       REG               1,18     1173952            19102973 /opt/homebrew/Cellar/libiconv/1.17/lib/libiconv.2.dylib
php-fpm   77376 mikhailgalanin  txt       REG               1,18     3430736           185506511 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/14.0.3/lib/darwin/libclang_rt.asan_osx_dynamic.dylib
php-fpm   77376 mikhailgalanin    0u      CHR                3,2         0t0                 335 /dev/null
php-fpm   77376 mikhailgalanin    1u      CHR                3,2         0t0                 335 /dev/null
php-fpm   77376 mikhailgalanin    2u      CHR              16,20   0t2140675                1359 /dev/ttys020
php-fpm   77376 mikhailgalanin    3u      CHR              16,20   0t2140675                1359 /dev/ttys020
php-fpm   77376 mikhailgalanin    4w      REG               1,18           0           227468843 /Users/mikhailgalanin/src/php-src/log/php-fpm.log
php-fpm   77376 mikhailgalanin    5u     unix  0xc97642ec9b68521         0t0                     ->0xc97642ec9b685e9
php-fpm   77376 mikhailgalanin    6u     unix  0xc97642ec9b685e9         0t0                     ->0xc97642ec9b68521
php-fpm   77376 mikhailgalanin    7u     IPv6  0xc97643865f6bfe9         0t0                 TCP *:8002 (LISTEN)
php-fpm   77376 mikhailgalanin    8u   KQUEUE                                                    count=0, state=0xa

Worker:

php-fpm   77377 mikhailgalanin  cwd       DIR               1,18        2080             3682735 /Users/mikhailgalanin/src/php-src
php-fpm   77377 mikhailgalanin  txt       REG               1,18    50481108           227463483 /Users/mikhailgalanin/src/php-src/sapi/fpm/php-fpm
php-fpm   77377 mikhailgalanin  txt       REG               1,18     1173952            19102973 /opt/homebrew/Cellar/libiconv/1.17/lib/libiconv.2.dylib
php-fpm   77377 mikhailgalanin  txt       REG               1,18     3430736           185506511 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/14.0.3/lib/darwin/libclang_rt.asan_osx_dynamic.dylib
php-fpm   77377 mikhailgalanin  txt       REG               1,15  1591853056              121701 /System/Volumes/Preboot/Cryptexes/OS/System/Library/dyld/dyld_shared_cache_arm64e
php-fpm   77377 mikhailgalanin    0u      CHR                3,2         0t0                 335 /dev/null
php-fpm   77377 mikhailgalanin    1u      CHR                3,2         0t0                 335 /dev/null
php-fpm   77377 mikhailgalanin    2u      CHR                3,2         0t0                 335 /dev/null
php-fpm   77377 mikhailgalanin    3u      CHR              16,20   0t2140675                1359 /dev/ttys020
php-fpm   77377 mikhailgalanin    8u     IPv6  0xc97643865f6bfe9         0t0                 TCP *:8002 (LISTEN)

[mikhainin]

Hi @bukka,

I just checked the issues you mentioned and it looks like the main concern (listening socket = stdin) appeared by mistake. It doesn't seem to happen on Linux or MacOS.

I added a test and also set CLOEXEC on the accepted socket in the FPM worker (which also leaked).

[bukka]

@mikhainin Finally got time to properly test it. I have done some modifications in couple of places but in general it was good. All merged now.

[andypost]

Filed follow-up as the test is borked for Alpinelinux #12077