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This is a simpler and more general solution to the problem so far solved by
osmo_fsm_term_safely(true). This extends use-after-free fixes to arbitrary
functions, not only FSM instances during termination.
The aim is to defer talloc_free() until back in the main loop.
Rationale: I discovered an osmo-msc use-after-free crash from an invalid
message, caused by this pattern:
void event_action()
{
osmo_fsm_inst_dispatch(foo, FOO_EVENT, NULL);
osmo_fsm_inst_dispatch(bar, BAR_EVENT, NULL);
}
Usually, FOO_EVENT takes successful action, and afterwards we also notify bar.
However, in this particular case, FOO_EVENT caused failure, and the immediate
error handling directly terminated and deallocated bar. In such a case,
dispatching BAR_EVENT causes a use-after-free; this constituted a DoS vector
just from sending messages that cause *any* failure during the first event
dispatch.
Instead, when this is enabled, we do not deallocate 'foo' until event_action()
has returned back to the main loop.
Test: duplicate fsm_dealloc_test.c using this, and print the number of items
deallocated in each test loop, to ensure the feature works. We also verify that
the deallocation safety works simply by fsm_dealloc_test.c not crashing.
We should probably follow up by refusing event dispatch and state transitions
for FSM instances that are terminating or already terminated:
see I0adc13a1a998e953b6c850efa2761350dd07e03a.
Change-Id: Ief4dba9ea587c9b4aea69993e965fbb20fb80e78
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A separate ST_DESTROYING state originally helped with certain deallocation
scenarios. But now that fsm.c avoids re-entering osmo_fsm_inst_term() twice and
gracefully handles FSM instance deallocations for termination cascades, it is
actually just as safe without a separate ST_DESTROYING state. ST_DESTROYING was
used to flag deallocation and prevent entering osmo_fsm_inst_term() twice,
which works only in a very limited range of scenarios.
Remove ST_DESTROYING from fsm_dealloc_test.c to show that all tested scenarios
still clean up gracefully.
Change-Id: I05354e6cad9b82ba474fa50ffd41d481b3c697b4
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Add global flag osmo_fsm_term_safely() -- if set to true, enable the following
behavior:
Detect osmo_fsm_inst_term() occuring within osmo_fsm_inst_term():
- collect deallocations until the outermost osmo_fsm_inst_term() is done.
- call osmo_fsm_inst_free() *after* dispatching the parent event.
If a struct osmo_fsm_inst enters osmo_fsm_inst_term() while another is already
within osmo_fsm_inst_term(), do not directly deallocate it, but talloc-reparent
it to a separate talloc context, to be deallocated with the outermost FSM inst.
The effect is that all osmo_fsm_inst freed within an osmo_fsm_inst_term()
cascade will stay allocated until all osmo_fsm_inst_term() are complete and all
of them will be deallocated at the same time.
Mark the deferred deallocation state as __thread in an attempt to make cascaded
deallocation handling threadsafe. Keep the enable/disable flag separate, so
that it is global and not per-thread.
The feature is showcased by fsm_dealloc_test.c: with this feature, all of those
wild deallocation scenarios succeed.
Make fsm_dealloc_test a normal regression test in testsuite.at.
Rationale:
It is difficult to gracefully handle deallocations of groups of FSM instances
that reference each other. As soon as one child dispatching a cleanup event
causes its parent to deallocate before fsm.c was ready for it, deallocation
will hit a use-after-free. Before this patch, by using parent_term events and
distinct "terminating" FSM states, parent/child FSMs can be taught to wait for
all children to deallocate before deallocating the parent. But as soon as a
non-child / non-parent FSM instance is involved, or actually any other
cleanup() action that triggers parent FSMs or parent talloc contexts to become
unused, it is near impossible to think of all possible deallocation events
ricocheting, and to avoid running into freeing FSM instances that were still in
the middle of osmo_fsm_inst_term(), or FSM instances to enter
osmo_fsm_inst_term() more than once. This patch makes deallocation of "all
possible" setups of complex cross referencing FSM instances easy to handle
correctly, without running into use-after-free or double free situations, and,
notably, without changing calling code.
Change-Id: I8eda67540a1cd444491beb7856b9fcd0a3143b18
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To prevent re-entering osmo_fsm_inst_term() twice for the same osmo_fsm_inst,
add flag osmo_fsm_inst.proc.terminating. osmo_fsm_inst_term() sets this to
true, or exits if it already is true.
Update fsm_dealloc_test.err for illustration. It is not relevant for unit
testing yet, just showing the difference.
Change-Id: I0c02d76a86f90c49e0eae2f85db64704c96a7674
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Despite efforts to properly handle "GONE" events and entering a ST_DESTROYING
only once, so far this test runs straight into a heap use-after-free. With
current fsm.c, it is hard to resolve the situation with the objects named
"other" also causing deallocations besides the FSM instance parent/child
relations.
For illustration, add an "expected" test output file fsm_dealloc_test.err,
making this pass will follow in a subsequent patch.
Change-Id: If801907c541bca9f524c9e5fd22ac280ca16979a
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Add a flag that adds timeout info to osmo_fsm_inst state change logging.
To not affect unit testing, make this an opt-in feature that is disabled by
default -- mostly because osmo_fsm_inst_state_chg_keep_timer() will produce
non-deterministic logging depending on timing (logs remaining time).
Unit tests that don't verify log output and those that use fake time may also
enable this feature. Do so in fsm_test.c.
The idea is that in due course we will add osmo_fsm_log_timeouts(true) calls to
all of our production applications' main() initialization.
Change-Id: I089b81021a1a4ada1205261470da032b82d57872
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Before this patch, if timeout_secs == 0 was passed to
osmo_fsm_inst_state_chg(), the previous T value remained set in the
osmo_fsm_inst->T.
For example:
osmo_fsm_inst_state_chg(fi, ST_X, 23, 42);
// timer == 23 seconds; fi->T == 42
osmo_fsm_inst_state_chg(fi, ST_Y, 0, 0);
// no timer; fi->T == 42!
Instead, always set to the T value passed to osmo_fsm_inst_state_chg().
Adjust osmo_fsm_inst_state_chg() API doc; need to rephrase to accurately
describe the otherwise unchanged behaviour independently from T.
Verify in fsm_test.c.
Rationale: it is confusing to have a T number remaining from some past state,
especially since the user explicitly passed a T number to
osmo_fsm_inst_state_chg(). (Usually we are passing timeout_secs=0, T=0).
I first thought this behavior was introduced with
osmo_fsm_inst_state_chg_keep_timer(), but in fact osmo_fsm_inst_state_chg()
behaved this way from the start.
This shows up in the C test for the upcoming tdef API, where the test result
printout was showing some past T value sticking around after FSM state
transitions. After this patch, there will be no such confusion.
Change-Id: I65c7c262674a1bc5f37faeca6aa0320ab0174f3c
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Change-Id: I3c0e53b846b2208bd201ace99777f2286ea39ae8
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In the osmo-msc, I would like to set the subscr conn FSM identifier by a string
format, to include the type of Complete Layer 3 that is taking place. I could
each time talloc a string and free it again. This API is more convenient.
From osmo_fsm_inst_update_id(), call osmo_fsm_inst_update_id_f() with "%s" (or
pass NULL).
Put the name updating into separate static update_name() function to clarify.
Adjust the error message for erratic ID: don't say "allocate", it might be from
an update. Adjust test expectation.
Change-Id: I76743a7642f2449fd33350691ac8ebbf4400371d
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On erratic id in osmo_fsm_inst_update_id(), don't say "Attempting to allocate
FSM instance".
Escape the invalid id using osmo_quote_str().
Change-Id: I770fc460de21faa42b403f694e853e8da01c4bef
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Since alloc relies on osmo_fsm_inst_update_id() to set the name, never skip
that.
In osmo_fsm_inst_alloc(), we allow passing a NULL id, and in
osmo_fsm_inst_update_id(), we set the name without id if id is NULL.
Change-Id: I6d6b09a811b82770818f19b189a57d9fc4a8133b
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Place id and name testing in its separate section, test_id_api().
Add a test that actually allocates an FSM instance with a NULL id, which is
allowed, but uncovers a bug of an unset FSM instance name. osmo_fsm_inst_name()
falls back to the fsm struct's name on NULL, but osmo_fsm_inst_find_by_name()
fails to match if the instance's name is NULL (and until recently even
crashed). Show this in fsm_test.c with loud comments.
Add test to clear the id by passing NULL.
Add test for setting an empty id.
Add test for setting an invalid identifier (osmo_identifier_valid() == false).
Change-Id: I646ed918576ce196c395dc5f42a1507c52ace2c5
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In fsm_test.c, we have FSM instance cleanup after the select main loop, but we
exit(0) in the timer cb; hence the final code is never called.
Rather clean up the instance and hence also test that, by using a global flag
to exit the main loop upon timeout.
Adjust expected stderr output.
BTW, in a subsequent commit, I want to move the fsm instance id testing to
below the main loop, to more clearly group the tested bits.
Change-Id: Ia47811ffcc1bd68d2630c86be7ab98fc1f338773
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If the name stays the same the log messages will still log with the old
id. Since we can now change the id we need to update the name as well.
NULL as id was allowed before so we should allow that as well.
Change-Id: I6b01eb10b8a05fee3e4a5cdefdcf3ce9f79545b4
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Event names are displayed in VTY commands so all FSM should have them.
Print an error message if an FSM is registered without event names.
We could also return an error code, however at present no caller checks
the return value of osmo_fsm_register() so this would be pointless.
Add event names to the test FSM and update expected output accordingly.
Change-Id: I08b100d62b5c50bf025ef87d31ea39072539cf37
Related: OS#3008
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Change-Id: Ic3d5da00f7ece6dbcd4c999187a5748c9331e60f
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This allows programmatic access to introspection of FSM instances, which
is quite handy from e.g. external test cases: Send a message to the
code, then use the CTRL interface to check if that message has triggered
the right kind of state transition.
Change-Id: I0f80340ee9c61c88962fdd6764a6098a844d0d1e
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Introduce two lookup helper functions to resolve a fsm_instance based on
the FSM and name or ID. Also, add related test cases.
Change-Id: I707f3ed2795c28a924e64adc612d378c21baa815
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Change-Id: Ifd7e85cd69b5e7e473000abc1ef7a56748aafc0e
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Provide one central LOGPFSML to print FSM information, take the FSM logging
subsystem from the FSM instance but use an explicitly provided log level
instead of the FSM's default level.
Use to replace some, essentially, duplications of the LOGPFSM macro.
In effect, the fsm_test's expected error changes, since the previous code dup
for logging events used round braces to indicate the fi's state, while the
central macro uses curly braces.
Change-Id: If295fdabb3f31a0fd9490d1e0df57794c75ae547
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osmo_fsm_inst_alloc() logs allocation but osmo_fsm_inst_free() is
silent. Fix this by adding log message for deallocation to make FSM
lifecycle tracking easier. Also make sure it's covered by test suite.
Change-Id: I7e5b55a1fff8e36cf61c7fb61d3e79c1f00e29d2
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Previously function was defined but not exposed so there were a way to
register FSM but no way to unregister it.
Change-Id: I2e749d896009784b77d6d5952fcc38e1c131db2b
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This code is supposed to formalize some of the state machine handling in
Osmocom code.
Change-Id: I0b0965a912598c1f6b84042a99fea9d522642466
Reviewed-on: https://gerrit.osmocom.org/163
Tested-by: Jenkins Builder
Reviewed-by: Harald Welte <laforge@gnumonks.org>
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