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List:       freebsd-jail
Subject:    [Bug 278195] daemon in jail is exiting without informing that it failed to execute
From:       bugzilla-noreply () freebsd ! org
Date:       2024-04-08 6:51:25
Message-ID: bug-278195-29815-yxPdxxcljS () https ! bugs ! freebsd ! org/bugzilla/
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=278195

--- Comment #3 from Zhenlei Huang <zlei@FreeBSD.org> ---
Another truss(1) that show what happens when the `--close-fds` option is
supplied.

```
# truss -f /tmp/daemon -fSl daemon echo OK
..
  955: connect(3,{ AF_UNIX "/var/run/logpriv" },106) = 0 (0x0)
  955: open("/dev/null",O_RDWR,00)               = 4 (0x4)
  955: sigaction(SIGHUP,{ SIG_IGN 0x0 ss_t },{ SIG_IGN SA_RESTART ss_t }) = 0
(0x0)
  956: <new process>
  955: fork()                                    = 956 (0x3bc)
  956: setsid()                                  = 956 (0x3bc)
  956: sigaction(SIGHUP,{ SIG_IGN SA_RESTART ss_t },0x0) = 0 (0x0)
  956: dup2(4,0)                                 = 0 (0x0)
  956: dup2(4,1)                                 = 1 (0x1)
  956: dup2(4,2)                                 = 2 (0x2)
  956: close(4)                                  = 0 (0x0)
  956: madvise(0x0,0,MADV_PROTECT)               = 0 (0x0)
  956: pipe2(0x7fffffffe950,0)                   = 0 (0x0)
  956: write(2,"ld-elf.so.1: ",13)               = 13 (0xd)
  956: write(2,"/tmp/daemon: Undefined symbol "k"...,48) = 48 (0x30)
  956: write(2,"\n",1)                           = 1 (0x1)
  956: exit(0x1)                                
  956: process exit, rval = 1
  955: exit(0x0)                                
  955: process exit, rval = 0
```

So simply put, when `--close-fds` option is present, daemon(3) closes fd 0,1,2
and these fds are redirected to /dev/null but logfile or syslog is opened too
late to catch error messages.

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