[tor-bugs] #15088 [Tor]: Add the wait4() syscall to the seccomp sandbox

[Tor Bug Tracker & Wiki]

#15088: Add the wait4() syscall to the seccomp sandbox
--------------------+-------------------------------
 Reporter:  sanic   |          Owner:
     Type:  defect  |         Status:  new
 Priority:  normal  |      Milestone:
Component:  Tor     |        Version:  Tor: 0.2.5.10
 Keywords:          |  Actual Points:
Parent ID:          |         Points:
--------------------+-------------------------------
 Tor version 0.2.5.10 seems to call wait4() upon receiving SIGHUP, and this
 violates the seccomp sandbox rules in sandbox.c, crashing the tor process.

 Trace from tor's log on debug loglevel, right after {{{/etc/init.d/tor
 reload}}}:
 {{{
 ============================================================ T= 1425215692
 (Sandbox) Caught a bad syscall attempt (syscall wait4)
 /usr/bin/tor(+0x12f4f1)[0x4273cf44f1]
 /lib64/libc.so.6(waitpid+0x1a)[0x3423957b1da]
 /lib64/libc.so.6(waitpid+0x1a)[0x3423957b1da]
 /usr/bin/tor(notify_pending_waitpid_callbacks+0x4a)[0x4273cf42da]
 /usr/bin/tor(process_signal+0x4ad)[0x4273bfb96d]
 /usr/lib64/libevent-2.0.so.5(event_base_loop+0x99e)[0x3423a111a6e]
 /usr/bin/tor(do_main_loop+0x1ad)[0x4273bfa77d]
 /usr/bin/tor(tor_main+0x1875)[0x4273bfd755]
 /lib64/libc.so.6(__libc_start_main+0xf5)[0x342394e2d55]
 /usr/bin/tor(+0x31c49)[0x4273bf6c49]
 Mar 01 16:14:52.000 [info] cpuworker_main(): read request failed. Exiting.
 }}}

 The patch is as simple as adding wait4() to the whitelist:
 {{{
 diff -Naur tor-0.2.5.10/src/common/sandbox.c
 tor-0.2.5.10.new/src/common/sandbox.c
 --- tor-0.2.5.10/src/common/sandbox.c
 +++ tor-0.2.5.10.new/src/common/sandbox.c
 @@ -119,6 +119,7 @@
      SCMP_SYS(epoll_wait),
      SCMP_SYS(fcntl),
      SCMP_SYS(fstat),
 +    SCMP_SYS(wait4),
  #ifdef __NR_fstat64
      SCMP_SYS(fstat64),
  #endif
 }}}

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/15088>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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