Fatal error on executing a hook (permissions?)

[Zverik]

I'm not sure what is happening. My hooks file:

[[hooks]]
folder = "/opt/sync/zettel"
event = "folder_down_sync_done"
allow_concurrent = false
command = "/srv/update_izv.sh"

I have done sudo -u <stfed_user> /srv/update_izv.sh from a random directory, worked file.

I'm running stfed as a systemd service. Here is an excerpt from its log after we got an update:

Jan 10 17:54:23 zverev stfed[547730]: Host: 127.0.0.1:8384
Jan 10 17:54:23 zverev stfed[547730]: User-Agent: stfed/1.1.0
Jan 10 17:54:23 zverev stfed[547730]: Accept: */*
Jan 10 17:54:23 zverev stfed[547730]: X-API-Key: REMOVED
Jan 10 17:54:23 zverev stfed[547730]: DEBUG [ureq::response] Chunked body in response
Jan 10 17:54:23 zverev stfed[547730]: DEBUG [ureq::unit] response 200 to GET http://127.0.0.1:8384/rest/events?since=13&limit=1&events=ItemFinished%2CFolderSummary%2CLocalChangeDetected%2CConfigS>
Jan 10 17:54:23 zverev stfed[547730]: DEBUG [ureq::pool] adding stream to pool: http|127.0.0.1|8384 -> Stream(TcpStream { addr: 127.0.0.1:41836, peer: 127.0.0.1:8384, fd: 3 })
Jan 10 17:54:23 zverev stfed[547730]: INFO  [stfed] New event: FolderDownSyncDone { folder: "/opt/sync/zettel" }
Jan 10 17:54:23 zverev stfed[547730]: INFO  [stfed::hook] Running hook: FolderHook { folder: "/opt/sync/zettel", event: FolderDownSyncDone, filter: None, command: ["/srv/update_izv.sh"], allow_concurrent: Some(false) } with path None and folder "/opt/sync/zettel"
Jan 10 17:54:23 zverev stfed[547730]: DEBUG [stfed::syncthing] GET "http://127.0.0.1:8384/rest/events?since=14&limit=1&events=ItemFinished%2CFolderSummary%2CLocalChangeDetected%2CConfigSaved&timeout=3600
Jan 10 17:54:23 zverev stfed[547730]: DEBUG [ureq::pool] pulling stream from pool: http|127.0.0.1|8384 -> Stream(TcpStream { addr: 127.0.0.1:41836, peer: 127.0.0.1:8384, fd: 3 })
Jan 10 17:54:23 zverev stfed[547730]: DEBUG [ureq::unit] sending request (reused connection) GET http://127.0.0.1:8384/rest/events?since=14&limit=1&events=ItemFinished%2CFolderSummary%2CLocalChan>
Jan 10 17:54:23 zverev stfed[547730]: DEBUG [ureq::unit] writing prelude: GET /rest/events?since=14&limit=1&events=ItemFinished%2CFolderSummary%2CLocalChangeDetected%2CConfigSaved&timeout=3600 HT>
Jan 10 17:54:23 zverev stfed[547730]: Host: 127.0.0.1:8384
Jan 10 17:54:23 zverev stfed[547730]: User-Agent: stfed/1.1.0
Jan 10 17:54:23 zverev stfed[547730]: Accept: */*
Jan 10 17:54:23 zverev stfed[547730]: X-API-Key: REMOVED
Jan 10 17:54:23 zverev stfed[547730]: DEBUG [ureq::response] Chunked body in response
Jan 10 17:54:23 zverev stfed[547730]: DEBUG [ureq::unit] response 200 to GET http://127.0.0.1:8384/rest/events?since=14&limit=1&events=ItemFinished%2CFolderSummary%2CLocalChangeDetected%2CConfigS>
Jan 10 17:54:23 zverev stfed[547851]: #
Jan 10 17:54:23 zverev stfed[547851]: # Fatal error in , line 0
Jan 10 17:54:23 zverev stfed[547851]: # Check failed: 12 == (*__errno_location ()).
Jan 10 17:54:23 zverev stfed[547851]: #
Jan 10 17:54:23 zverev stfed[547851]: #
Jan 10 17:54:23 zverev stfed[547851]: #
Jan 10 17:54:23 zverev stfed[547851]: #FailureMessage Object: 0x7ffeecdce390
Jan 10 17:54:23 zverev stfed[547851]: ----- Native stack trace -----
Jan 10 17:54:23 zverev stfed[547851]:  1: 0x101c1a1  [node]
Jan 10 17:54:23 zverev stfed[547851]:  2: 0x27bb9eb V8_Fatal(char const*, ...) [node]
Jan 10 17:54:23 zverev stfed[547851]:  3: 0x27c6ba7 v8::base::OS::SetPermissions(void*, unsigned long, v8::base::OS::MemoryPermission) [node]
Jan 10 17:54:23 zverev stfed[547851]:  4: 0x14ea4c5 v8::internal::MemoryAllocator::SetPermissionsOnExecutableMemoryChunk(v8::internal::VirtualMemory*, unsigned long, unsigned long, unsigned long)>
Jan 10 17:54:23 zverev stfed[547851]:  5: 0x14ea7e1 v8::internal::MemoryAllocator::AllocateAlignedMemory(unsigned long, unsigned long, unsigned long, v8::internal::AllocationSpace, v8::internal::>
Jan 10 17:54:23 zverev stfed[547851]:  6: 0x14eaa54 v8::internal::MemoryAllocator::AllocateUninitializedChunkAt(v8::internal::BaseSpace*, unsigned long, v8::internal::Executability, unsigned long>
Jan 10 17:54:23 zverev stfed[547851]:  7: 0x14eac5c v8::internal::MemoryAllocator::AllocatePage(v8::internal::MemoryAllocator::AllocationMode, v8::internal::Space*, v8::internal::Executability) [>
Jan 10 17:54:23 zverev stfed[547851]:  8: 0x15082a0 v8::internal::PagedSpaceBase::TryExpand(v8::internal::LocalHeap*, v8::internal::AllocationOrigin) [node]
Jan 10 17:54:23 zverev stfed[547851]:  9: 0x14b7413 v8::internal::PagedSpaceAllocatorPolicy::RefillLab(int, v8::internal::AllocationOrigin) [node]
Jan 10 17:54:23 zverev stfed[547851]: 10: 0x14b55db v8::internal::MainAllocator::AllocateRawSlow(int, v8::internal::AllocationAlignment, v8::internal::AllocationOrigin) [node]
Jan 10 17:54:23 zverev stfed[547851]: 11: 0x14548d6 v8::internal::Factory::CodeBuilder::AllocateUninitializedInstructionStream(bool) [node]
Jan 10 17:54:23 zverev stfed[547851]: 12: 0x146c509 v8::internal::Factory::CodeBuilder::BuildInternal(bool) [node]
Jan 10 17:54:23 zverev stfed[547851]: 13: 0x19e2172 v8::internal::baseline::BaselineCompiler::Build(v8::internal::LocalIsolate*) [node]
Jan 10 17:54:23 zverev stfed[547851]: 14: 0x12b0daa v8::internal::GenerateBaselineCode(v8::internal::Isolate*, v8::internal::Handle<v8::internal::SharedFunctionInfo>) [node]
Jan 10 17:54:23 zverev stfed[547851]: 15: 0x130f81b v8::internal::Compiler::CompileSharedWithBaseline(v8::internal::Isolate*, v8::internal::Handle<v8::internal::SharedFunctionInfo>, v8::internal:>
Jan 10 17:54:23 zverev stfed[547851]: 16: 0x130fac2 v8::internal::Compiler::CompileBaseline(v8::internal::Isolate*, v8::internal::Handle<v8::internal::JSFunction>, v8::internal::Compiler::ClearEx>
Jan 10 17:54:23 zverev stfed[547851]: 17: 0x19df60b v8::internal::baseline::BaselineBatchCompiler::CompileBatch(v8::internal::Handle<v8::internal::JSFunction>) [node]
Jan 10 17:54:23 zverev stfed[547851]: 18: 0x13fb36f v8::internal::TieringManager::OnInterruptTick(v8::internal::Handle<v8::internal::JSFunction>, v8::internal::CodeKind) [node]
Jan 10 17:54:23 zverev stfed[547851]: 19: 0x18b460b  [node]
Jan 10 17:54:23 zverev stfed[547851]: 20: 0x18b6254 v8::internal::Runtime_BytecodeBudgetInterruptWithStackCheck_Ignition(int, unsigned long*, v8::internal::Isolate*) [node]
Jan 10 17:54:23 zverev stfed[547851]: 21: 0x1e12476  [node]
Jan 10 17:54:23 zverev stfed[547850]: Trace/breakpoint trap (core dumped)
Jan 10 17:54:24 zverev stfed[547730]: INFO  [stfed::hook] Process exited with code Some(133)

[desbma]

Does your systemd service has hardening options set?
stfed does nothing special when executing the command, apart from closing stdin.

EDIT: I have taken the liberty to edit the log have posted, because it had your Syncthing API key in clear text.

[desbma]

v8::internal::MemoryAllocator::SetPermissionsOnExecutableMemoryChunk

From this I think it's highly likely that systemd hardening is causing your v8 based program to crash.
Try commenting out MemoryDenyWriteExecute=true in the stfed service file.

[Zverik]

Yaaay, it helped! Setting the parameter to false made the error go away. Thank you Maxime!

(I have also changed my API key.)