fix loop on packets with pseudo dns types
NixOS/systemd#14

fix loop on packets with pseudo dns types
NixOS/systemd#14

(cherry picked from commit 94cba39)

Fuzzing with AddressSanitizer reports an error here:
==11==ERROR: AddressSanitizer: global-buffer-overflow on address 0x7fe53f5497d8 at pc 0x7fe53ef055c9 bp 0x7ffd344e9380 sp 0x7ffd344e9378
READ of size 4 at 0x7fe53f5497d8 thread T0
SCARINESS: 27 (4-byte-read-global-buffer-overflow-far-from-bounds)
    #0 0x7fe53ef055c8 in bus_error_name_to_errno /work/build/../../src/systemd/src/libsystemd/sd-bus/bus-error.c:118:24
    #1 0x7fe53ef0577b in bus_error_setfv /work/build/../../src/systemd/src/libsystemd/sd-bus/bus-error.c:274:17
    #2 0x7fe53ef0595a in sd_bus_error_setf /work/build/../../src/systemd/src/libsystemd/sd-bus/bus-error.c:284:21
    #3 0x561059 in manager_load_unit_prepare /work/build/../../src/systemd/src/core/manager.c
    #4 0x560680 in manager_load_unit /work/build/../../src/systemd/src/core/manager.c:1773:13
    #5 0x5d49a6 in unit_add_dependency_by_name /work/build/../../src/systemd/src/core/unit.c:2882:13
    #6 0x538996 in config_parse_unit_deps /work/build/../../src/systemd/src/core/load-fragment.c:152:21
    #7 0x6db771 in next_assignment /work/build/../../src/systemd/src/shared/conf-parser.c:155:32
    #8 0x6d697e in parse_line /work/build/../../src/systemd/src/shared/conf-parser.c:273:16
    #9 0x6d5c48 in config_parse /work/build/../../src/systemd/src/shared/conf-parser.c:390:21
    #10 0x535678 in LLVMFuzzerTestOneInput /work/build/../../src/systemd/src/fuzz/fuzz-unit-file.c:41:16
    #11 0x73bd60 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/libfuzzer/FuzzerLoop.cpp:517:13
    #12 0x73a39f in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /src/libfuzzer/FuzzerLoop.cpp:442:3
    #13 0x73d9bc in fuzzer::Fuzzer::MutateAndTestOne() /src/libfuzzer/FuzzerLoop.cpp:650:19
    #14 0x73fa05 in fuzzer::Fuzzer::Loop(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:773:5
    #15 0x71f75d in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/libfuzzer/FuzzerDriver.cpp:754:6
    #16 0x71285c in main /src/libfuzzer/FuzzerMain.cpp:20:10
    #17 0x7fe53da0482f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #18 0x430e68 in _start (/out/fuzz-unit-file+0x430e68)

0x7fe53f5497d8 is located 8 bytes to the right of global variable 'bus_common_errors' defined in '../../src/systemd/src/libsystemd/sd-bus/bus-common-errors.c:28:51' (0x7fe53f549300) of size 1232
SUMMARY: AddressSanitizer: global-buffer-overflow /work/build/../../src/systemd/src/libsystemd/sd-bus/bus-error.c:118:24 in bus_error_name_to_errno
Shadow bytes around the buggy address:
  0x0ffd27ea12a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffd27ea12b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffd27ea12c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffd27ea12d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffd27ea12e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0ffd27ea12f0: 00 00 00 00 00 00 00 00 00 00 f9[f9]f9 f9 f9 f9
  0x0ffd27ea1300: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
  0x0ffd27ea1310: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
  0x0ffd27ea1320: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffd27ea1330: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffd27ea1340: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==11==ABORTING

but I think it's a false positive because of our low-level magic in how this
area is constructed.

`fuzz-journal-remote` seems to be failing under `msan` as soon as it starts:

$ sudo infra/helper.py run_fuzzer systemd fuzz-journal-remote
Running: docker run --rm -i --privileged -e FUZZING_ENGINE=libfuzzer -v /home/vagrant/oss-fuzz/build/out/systemd:/out -t gcr.io/oss-fuzz-base/base-runner run_fuzzer fuzz-journal-remote
Using seed corpus: fuzz-journal-remote_seed_corpus.zip
/out/fuzz-journal-remote -rss_limit_mb=2048 -timeout=25 /tmp/fuzz-journal-remote_corpus -max_len=65536 < /dev/null
INFO: Seed: 3380449479
INFO: Loaded 2 modules   (36336 inline 8-bit counters): 36139 [0x7ff36ea31d39, 0x7ff36ea3aa64), 197 [0x9998c8, 0x99998d),
INFO: Loaded 2 PC tables (36336 PCs): 36139 [0x7ff36ea3aa68,0x7ff36eac7d18), 197 [0x999990,0x99a5e0),
INFO:        2 files found in /tmp/fuzz-journal-remote_corpus
INFO: seed corpus: files: 2 min: 4657b max: 7790b total: 12447b rss: 97Mb
Uninitialized bytes in __interceptor_pwrite64 at offset 24 inside [0x7fffdd4d7230, 240)
==15==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x7ff36e685e8a in journal_file_init_header /work/build/../../src/systemd/src/journal/journal-file.c:436:13
    #1 0x7ff36e683a9d in journal_file_open /work/build/../../src/systemd/src/journal/journal-file.c:3333:21
    #2 0x7ff36e68b8f6 in journal_file_open_reliably /work/build/../../src/systemd/src/journal/journal-file.c:3520:13
    #3 0x4a3f35 in open_output /work/build/../../src/systemd/src/journal-remote/journal-remote.c:70:13
    #4 0x4a34d0 in journal_remote_get_writer /work/build/../../src/systemd/src/journal-remote/journal-remote.c:136:21
    #5 0x4a550f in get_source_for_fd /work/build/../../src/systemd/src/journal-remote/journal-remote.c:183:13
    #6 0x4a46bd in journal_remote_add_source /work/build/../../src/systemd/src/journal-remote/journal-remote.c:235:13
    #7 0x4a271c in LLVMFuzzerTestOneInput /work/build/../../src/systemd/src/fuzz/fuzz-journal-remote.c:36:9
    #8 0x4f27cc in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/libfuzzer/FuzzerLoop.cpp:524:13
    #9 0x4efa0b in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /src/libfuzzer/FuzzerLoop.cpp:448:3
    #10 0x4f8e96 in fuzzer::Fuzzer::ReadAndExecuteSeedCorpora(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:732:7
    #11 0x4f9f73 in fuzzer::Fuzzer::Loop(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:752:3
    #12 0x4bf329 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/libfuzzer/FuzzerDriver.cpp:756:6
    #13 0x4ac391 in main /src/libfuzzer/FuzzerMain.cpp:20:10
    #14 0x7ff36d14982f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #15 0x41f9d8 in _start (/out/fuzz-journal-remote+0x41f9d8)

  Uninitialized value was stored to memory at
    #0 0x7ff36e61cd41 in sd_id128_randomize /work/build/../../src/systemd/src/libsystemd/sd-id128/sd-id128.c:288:16
    #1 0x7ff36e685cec in journal_file_init_header /work/build/../../src/systemd/src/journal/journal-file.c:426:13
    #2 0x7ff36e683a9d in journal_file_open /work/build/../../src/systemd/src/journal/journal-file.c:3333:21
    #3 0x7ff36e68b8f6 in journal_file_open_reliably /work/build/../../src/systemd/src/journal/journal-file.c:3520:13
    #4 0x4a3f35 in open_output /work/build/../../src/systemd/src/journal-remote/journal-remote.c:70:13
    #5 0x4a34d0 in journal_remote_get_writer /work/build/../../src/systemd/src/journal-remote/journal-remote.c:136:21
    #6 0x4a550f in get_source_for_fd /work/build/../../src/systemd/src/journal-remote/journal-remote.c:183:13
    #7 0x4a46bd in journal_remote_add_source /work/build/../../src/systemd/src/journal-remote/journal-remote.c:235:13
    #8 0x4a271c in LLVMFuzzerTestOneInput /work/build/../../src/systemd/src/fuzz/fuzz-journal-remote.c:36:9
    #9 0x4f27cc in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/libfuzzer/FuzzerLoop.cpp:524:13
    #10 0x4efa0b in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /src/libfuzzer/FuzzerLoop.cpp:448:3
    #11 0x4f8e96 in fuzzer::Fuzzer::ReadAndExecuteSeedCorpora(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:732:7
    #12 0x4f9f73 in fuzzer::Fuzzer::Loop(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:752:3
    #13 0x4bf329 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/libfuzzer/FuzzerDriver.cpp:756:6
    #14 0x4ac391 in main /src/libfuzzer/FuzzerMain.cpp:20:10
    #15 0x7ff36d14982f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

  Uninitialized value was created by an allocation of 't' in the stack frame of function 'sd_id128_randomize'
    #0 0x7ff36e61cb00 in sd_id128_randomize /work/build/../../src/systemd/src/libsystemd/sd-id128/sd-id128.c:274

SUMMARY: MemorySanitizer: use-of-uninitialized-value /work/build/../../src/systemd/src/journal/journal-file.c:436:13 in journal_file_init_header
Exiting
MS: 0 ; base unit: 0000000000000000000000000000000000000000
artifact_prefix='./'; Test unit written to ./crash-847911777b3096783f4ee70a69ab6d28380c810b
[vagrant@localhost oss-fuzz]$ sudo infra/helper.py check_build --sanitizer=memory systemd
Running: docker run --rm -i --privileged -e FUZZING_ENGINE=libfuzzer -e SANITIZER=memory -v /home/vagrant/oss-fuzz/build/out/systemd:/out -t gcr.io/oss-fuzz-base/base-runner test_all
INFO: performing bad build checks for /out/fuzz-dhcp-server.
INFO: performing bad build checks for /out/fuzz-journal-remote.
INFO: performing bad build checks for /out/fuzz-unit-file.
INFO: performing bad build checks for /out/fuzz-dns-packet.
4 fuzzers total, 0 seem to be broken (0%).
Check build passed.

It's a false positive which is most likely caused by
google/sanitizers#852. I think it could be got around
by avoiding `getrandom` when the code is compiled with `msan`

This function returns 0 on success and a negative value on failure. On success,
it writes the parsed action to the address passed in its third argument.

`bus_set_transient_emergency_action` does this:

 r = parse_emergency_action(s, system, &v);
 if (v < 0)
     // handle failure

However, `v` is not updated if the function fails, and this should be checking
`r` instead of `v`.

The result of this is that if an invalid failure (or success) action is
specified, systemd ends up creating the unit anyway and then misbehaves if it
tries to run the failure action because the action value comes from
uninitialized stack data. In my case, this resulted in a failed assertion:

 Program received signal SIGABRT, Aborted.
 0x00007fe52cca0d7f in raise () from /snap/usr/lib/libc.so.6
 (gdb) bt
 #0  0x00007fe52cca0d7f in raise () from /snap/usr/lib/libc.so.6
 #1  0x00007fe52cc8b672 in abort () from /snap/usr/lib/libc.so.6
 #2  0x00007fe52d66f169 in log_assert_failed_realm (realm=LOG_REALM_SYSTEMD, text=0x56177ab8e000 "action < _EMERGENCY_ACTION_MAX", file=0x56177ab8dfb8 "../src/core/emergency-action.c", line=33, func=0x56177ab8e2b0 <__PRETTY_FUNCTION__.14207> "emergency_action") at ../src/basic/log.c:795
 #3  0x000056177aa98cf4 in emergency_action (m=0x56177c992cb0, action=2059118610, options=(unknown: 0), reboot_arg=0x0, exit_status=1, reason=0x7ffdd2df4290 "unit run-u0.service failed") at ../src/core/emergency-action.c:33
 #4  0x000056177ab2b739 in unit_notify (u=0x56177c9eb340, os=UNIT_ACTIVE, ns=UNIT_FAILED, flags=(unknown: 0)) at ../src/core/unit.c:2504
 #5  0x000056177aaf62ed in service_set_state (s=0x56177c9eb340, state=SERVICE_FAILED) at ../src/core/service.c:1104
 #6  0x000056177aaf8a29 in service_enter_dead (s=0x56177c9eb340, f=SERVICE_SUCCESS, allow_restart=true) at ../src/core/service.c:1712
 #7  0x000056177aaf9233 in service_enter_signal (s=0x56177c9eb340, state=SERVICE_FINAL_SIGKILL, f=SERVICE_SUCCESS) at ../src/core/service.c:1854
 #8  0x000056177aaf921b in service_enter_signal (s=0x56177c9eb340, state=SERVICE_FINAL_SIGTERM, f=SERVICE_SUCCESS) at ../src/core/service.c:1852
 #9  0x000056177aaf8eb3 in service_enter_stop_post (s=0x56177c9eb340, f=SERVICE_SUCCESS) at ../src/core/service.c:1788
 #10 0x000056177aaf91eb in service_enter_signal (s=0x56177c9eb340, state=SERVICE_STOP_SIGKILL, f=SERVICE_SUCCESS) at ../src/core/service.c:1850
 #11 0x000056177aaf91bc in service_enter_signal (s=0x56177c9eb340, state=SERVICE_STOP_SIGTERM, f=SERVICE_FAILURE_EXIT_CODE) at ../src/core/service.c:1848
 #12 0x000056177aaf9759 in service_enter_running (s=0x56177c9eb340, f=SERVICE_FAILURE_EXIT_CODE) at ../src/core/service.c:1941
 #13 0x000056177ab005b7 in service_sigchld_event (u=0x56177c9eb340, pid=112, code=1, status=1) at ../src/core/service.c:3296
 #14 0x000056177aad84b5 in manager_invoke_sigchld_event (m=0x56177c992cb0, u=0x56177c9eb340, si=0x7ffdd2df48f0) at ../src/core/manager.c:2444
 #15 0x000056177aad88df in manager_dispatch_sigchld (source=0x56177c994710, userdata=0x56177c992cb0) at ../src/core/manager.c:2508
 #16 0x00007fe52d72f807 in source_dispatch (s=0x56177c994710) at ../src/libsystemd/sd-event/sd-event.c:2846
 #17 0x00007fe52d730f7d in sd_event_dispatch (e=0x56177c993530) at ../src/libsystemd/sd-event/sd-event.c:3229
 #18 0x00007fe52d73142e in sd_event_run (e=0x56177c993530, timeout=18446744073709551615) at ../src/libsystemd/sd-event/sd-event.c:3286
 #19 0x000056177aad9f71 in manager_loop (m=0x56177c992cb0) at ../src/core/manager.c:2906
 #20 0x000056177aa7c876 in invoke_main_loop (m=0x56177c992cb0, ret_reexecute=0x7ffdd2df4bff, ret_retval=0x7ffdd2df4c04, ret_shutdown_verb=0x7ffdd2df4c58, ret_fds=0x7ffdd2df4c70, ret_switch_root_dir=0x7ffdd2df4c48, ret_switch_root_init=0x7ffdd2df4c50, ret_error_message=0x7ffdd2df4c60) at ../src/core/main.c:1792
 #21 0x000056177aa7f251 in main (argc=2, argv=0x7ffdd2df4e78) at ../src/core/main.c:2573

Fix this by checking the correct variable.

We would not send the property because we'd call sd_bus_get_current_message()
which would return NULL. If there is no message, we cannot support /self or
/auto, but things are still OK if a path with a session name is given.

Traceback when the issue is triggered:

 #2  we'd call sd_bus_get_current_message() here, which would return NULL, and
     session_object_find() would immediately return 0.
 #3  0x00000000004289b7 in session_object_find (bus=0x9f1110, path=0xa160b0 "/org/freedesktop/login1/session/c2",
     interface=0x9efda0 "org.freedesktop.login1.Session", userdata=0x9852f0, found=0x7ffe3e975fe8, error=0x7ffe3e9760b0)
     at ../src/login/logind-session-dbus.c:620
 #4  0x00007ff74bfdde39 in node_vtable_get_userdata (bus=0x9f1110, path=0xa160b0 "/org/freedesktop/login1/session/c2",
     c=0x9f6d58, userdata=0x7ffe3e976070, error=0x7ffe3e9760b0) at ../src/libsystemd/sd-bus/bus-objects.c:37
 #5  0x00007ff74bfe49af in emit_properties_changed_on_interface (bus=0x9f1110,
     prefix=0xa133a0 "/org/freedesktop/login1/session", path=0xa160b0 "/org/freedesktop/login1/session/c2",
     interface=0x43f9f8 "org.freedesktop.login1.Session", require_fallback=true, found_interface=0x7ffe3e976163,
     names=0x7ffe3e9761b0) at ../src/libsystemd/sd-bus/bus-objects.c:2088
 #6  0x00007ff74bfe56a4 in sd_bus_emit_properties_changed_strv (bus=0x9f1110,
     path=0xa160b0 "/org/freedesktop/login1/session/c2", interface=0x43f9f8 "org.freedesktop.login1.Session",
     names=0x7ffe3e9761b0) at ../src/libsystemd/sd-bus/bus-objects.c:2291
 #7  0x00000000004292ea in session_send_changed (s=0xa16e10, properties=0x43ee27 "Active")
    at ../src/login/logind-session-dbus.c:730
 #8  0x0000000000424cd7 in seat_set_active (s=0x9ee280, session=0xa16e10) at ../src/login/logind-seat.c:249
 #9  0x00000000004251cf in seat_active_vt_changed (s=0x9ee280, vtnr=3) at ../src/login/logind-seat.c:361
 #10 0x000000000042547b in seat_read_active_vt (s=0x9ee280) at ../src/login/logind-seat.c:395
 #11 0x000000000040ab5c in manager_dispatch_console (s=0x9f0320, fd=8, revents=8, userdata=0x9852f0)
     at ../src/login/logind.c:588
 #12 0x00007ff74c042d5f in source_dispatch (s=0x9f0320) at ../src/libsystemd/sd-event/sd-event.c:2828
 #13 0x00007ff74c04469f in sd_event_dispatch (e=0x9ef340) at ../src/libsystemd/sd-event/sd-event.c:3241
 #14 0x00007ff74c044b58 in sd_event_run (e=0x9ef340, timeout=18446744073709551615)
     at ../src/libsystemd/sd-event/sd-event.c:3299
 #15 0x000000000040d7e8 in manager_run (m=0x9852f0) at ../src/login/logind.c:1186
 #16 0x000000000040db58 in run (argc=1, argv=0x7ffe3e976728) at ../src/login/logind.c:1234
 #17 0x000000000040dc30 in main (argc=1, argv=0x7ffe3e976728) at ../src/login/logind.c:1244

Fixes systemd#13437. Bug introduced in 3b92c08.