[tor-bugs] #16160 [Tor]: seccomp sandbox does not work on arm

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#16160: seccomp sandbox does not work on arm
--------------------+------------------------------
 Reporter:  ajs124  |          Owner:
     Type:  defect  |         Status:  new
 Priority:  normal  |      Milestone:
Component:  Tor     |        Version:  Tor: 0.2.6.7
 Keywords:          |  Actual Points:
Parent ID:          |         Points:
--------------------+------------------------------
 Tor v0.2.6.8 as shipped by arch linux arm (armv6h/raspberry pi) crashes
 when the seccomp sandbox is enabled with the following error:
 {{{
 ============================================================ T= 1432314730
 (Sandbox) Caught a bad syscall attempt (syscall 289)
 /usr/bin/tor(+0x13f734)[0xb6ee7734]
 /usr/lib/libc.so.6(__send+0x1c)[0xb69ac7ec]
 /usr/lib/libc.so.6(__send+0x1c)[0xb69ac7ec]
 }}}
 I started looking into the code and came up with the attached patch.
 Afterwards the error message is this:
 {{{
 ============================================================ T= 1432331214
 (Sandbox) Caught a bad syscall attempt (syscall eventfd2)
 /usr/bin/tor(+0x1402e4)[0xb6ef02e4]
 /usr/lib/libc.so.6(eventfd+0xc)[0xb696ca5c]
 /usr/lib/libc.so.6(eventfd+0xc)[0xb696ca5c]
 /usr/bin/tor(alert_sockets_create+0x98)[0xb6eda974]
 /usr/bin/tor(replyqueue_new+0x3c)[0xb6ef43c4]
 /usr/bin/tor(cpu_init+0xc4)[0xb6ea1360]
 /usr/bin/tor(do_main_loop+0x358)[0xb6dd9cac]
 /usr/bin/tor(tor_main+0x160)[0xb6ddb744]
 }}}

 Since I'm neither familiar with seccomp nor the tor codebase, this is
 where I gave up… I hope someone here can fix this.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16160>
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