setconfig: fix crash when a configvar outlives its plugin option - #9386
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ksedgwic wants to merge 1 commit into
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setconfig: fix crash when a configvar outlives its plugin option#9386ksedgwic wants to merge 1 commit into
ksedgwic wants to merge 1 commit into
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configvar_finalize_overrides() dereferences the result of opt_find_long() without checking for NULL. A configvar can outlive its option: stopping a plugin unregisters the plugin's options, but destroy_plugin_opt() only removes configvars created by `plugin start` parameters. A configvar created by an earlier setconfig, or read from a config file at boot, stays in memory naming an option that is no longer registered. Once such a stale configvar exists, the next setconfig of ANY option (builtin or plugin, persistent or transient) walks all configvars in configvar_finalize_overrides() and crashes: common/configvar.c:112 (configvar_finalize_overrides) lightningd/configs.c:337 (configvar_updated) lightningd/configs.c:530 (configvar_save) lightningd/configs.c:600 (setconfig_success) lightningd/configs.c:804 (json_setconfig) Observed in the field when a plugin was dynamically restarted as a newer build that dropped one of its options; the first setconfig after the restart killed lightningd. Skip configvars whose option is no longer registered: they override nothing. (This also avoids two such stale configvars falsely marking each other overridden, since both would map to NULL.) Changelog-Fixed: lightningd: crash on `setconfig` after a dynamically restarted plugin dropped an option.
Collaborator
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Duplicate of #9249 |
Collaborator
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Please let me know If any of your tests should be included in #9249, which was originally just a repro test PR. |
Collaborator
Author
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The test comes at it from a different code path, but doesn't add any coverage over what you've got so I don't think it's worth very much |
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A configvar from a config file or an earlier setconfig outlives its
option when a plugin stops: destroy_plugin_opt() only removes
plugin start configvars. The next setconfig of any option then
NULL-derefs in configvar_finalize_overrides(). Seen in the field
after a routine dynamic plugin upgrade that dropped an option.
NULL-guard the lookup and add a pytest reproducing the crash
(lightningd SIGSEGVs on the test without the fix).
Fixes #9385