[tor-bugs] #25440 [Core Tor]: Broken openat syscall in Sandbox mode

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#25440: Broken openat syscall in Sandbox mode
----------------------------+--------------------------------
     Reporter:  ageisp0lis  |      Owner:  (none)
         Type:  defect      |     Status:  new
     Priority:  Medium      |  Milestone:
    Component:  Core Tor    |    Version:  Tor: 0.3.3.3-alpha
     Severity:  Normal      |   Keywords:  sandbox
Actual Points:              |  Parent ID:
       Points:              |   Reviewer:
      Sponsor:              |
----------------------------+--------------------------------
 My version is 0.3.3.2-alpha (git-7b1d356bdb76607d).

 If relevant, I am running under Debian buster/sid amd64 KVM VPS with a
 4.14.24 kernel patched with grsecurity, and AppArmor enabled.


 {{{
 Mar 06 10:14:36.024 [notice] Tor 0.3.3.2-alpha (git-7b1d356bdb76607d)
 running on Linux with Libevent 2.1.8-stable, OpenSSL 1.1.0g, Zlib 1.2.8,
 Liblzma 5.2.2, and Libzstd 1.3.3.
 Mar 06 10:14:36.025 [notice] Tor can't help you if you use it wrong! Learn
 how to be safe at https://www.torproject.org/download/download#warning
 Mar 06 10:14:36.025 [notice] This version is not a stable Tor release.
 Expect more bugs than usual.
 Mar 06 10:14:36.025 [notice] Read configuration file "/etc/tor/torrc".
 Mar 06 10:14:36.029 [notice] Scheduler type KIST has been enabled.
 Mar 06 10:14:36.029 [notice] Opening Socks listener on 127.0.0.1:9050
 Mar 06 10:14:36.029 [notice] Opening DNS listener on 127.0.0.1:5353
 Mar 06 10:14:36.029 [notice] Opening Transparent pf/netfilter listener on
 127.0.0.1:9040
 Mar 06 10:14:36.029 [notice] Opening Control listener on 127.0.0.1:9051

 ============================================================ T= 1520360077
 (Sandbox) Caught a bad syscall attempt (syscall openat)
 tor(+0x1a57ea)[0x20b99917ea]
 /lib/x86_64-linux-gnu/libpthread.so.0(open64+0x4b)[0x38f248203ab]
 /lib/x86_64-linux-gnu/libpthread.so.0(open64+0x4b)[0x38f248203ab]
 tor(tor_open_cloexec+0x40)[0x20b9977a00]
 tor(start_writing_to_file+0x17a)[0x20b998b2ea]
 tor(+0x19f3cb)[0x20b998b3cb]
 tor(+0x19f518)[0x20b998b518]
 tor(or_state_save+0x15b)[0x20b98aa27b]
 tor(+0x5488b)[0x20b984088b]
 /usr/lib/x86_64-linux-gnu/libevent-2.1.so.6(+0x229ba)[0x38f25cbe9ba]
 /usr/lib/x86_64-linux-
 gnu/libevent-2.1.so.6(event_base_loop+0x5a7)[0x38f25cbf537]
 tor(do_main_loop+0x2b4)[0x20b9841604]
 tor(tor_run_main+0x1025)[0x20b9843ad5]
 tor(tor_main+0x3a)[0x20b983c09a]
 tor(main+0x19)[0x20b983be29]
 /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7)[0x38f24272a87]
 tor(_start+0x2a)[0x20b983be7a]

 }}}

 It is possible this error is either due to Tor, or it could be security
 hardening applied to my server. Let me know in any case... Could commit
 ea8e9f17f52877cc795f1792acb81d7fdaff6baf be relevant?

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25440>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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