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SEA: BlobDeserializer SIGSEGVs when fuse byte is set but no NODE_SEA_BLOB is present

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Avaliação

Dificuldade
2/5
Tempo estimado
1-3 horas
Facilidade para iniciantes
76/100
Tipo de issue
Bug
Clareza
Claramente especificada
Status de atividade
Ativa
Stack de tecnologia
cpp, linux, nodejs
Domínio
operating-systems

Direção de pesquisa

Comece em src/node_sea_bin.cc, em node::sea::FindSingleExecutableBlob(), e rastreie o resultado de postject_find_resource("NODE_SEA_BLOB", ...) antes que BlobDeserializer seja executado. Reproduza o problema com o comando fornecido para alternar o fuse e, em seguida, verifique se a ausência do blob produz um erro de inicialização claro e uma saída diferente de zero em vez de um SIGSEGV.

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Descrição

stale
Version

v26.1.0 (also reproduces on v25.6.0)

Platform

Linux arm64 (reproduced on Apple Silicon via Docker Desktop, but the SEGV is platform-independent)

Subsystem

sea

What steps will reproduce the bug?

Binaries where the postject fuse byte is set to 1 but NODE_SEA_BLOB cannot be located at runtime currently die with a NULL-deref SIGSEGV inside BlobDeserializer::ReadArithmetic, with no error message indicating the cause.

Take any Node binary, flip the fuse byte from 0 to 1 without injecting an actual SEA blob:

python3 -c "
sent = b'NODE_SEA_FUSE_fce680ab2cc467b6e072b8b5df1996b2'
with open('hello','rb') as f: buf = bytearray(f.read())
i = buf.find(sent)
buf[i + len(sent) + 1] = ord('1')
with open('hello','wb') as f: f.write(bytes(buf))
"
chmod +x hello
./hello --version    # → Segmentation fault, exit 139

This state arises naturally when postject is run against a host binary with no PT_NOTE program header — postject silently fails to inject the note but still flips the fuse byte. See https://github.com/nodejs/postject/issues/107 and https://github.com/nodejs/unofficial-builds/issues/200.

How often does it reproduce? Is there a required condition?

100% reproducible. Required condition: fuse byte set to 1 AND no NODE_SEA_BLOB discoverable via postject_find_resource().

What is the expected behavior? Why is that the expected behavior?

A clear error indicating that the SEA fuse is set but no blob is present, rather than a bare SIGSEGV at startup. The current behavior makes it look like a crash in OpenSSL or libc (because the SIGILLs from OpenSSL's ARM crypto-extension probes show up first under gdb), when the actual cause is much earlier and recoverable.

What do you see instead?
Program received signal SIGSEGV, Segmentation fault.
#0  memcpy ()
#1  node::BlobDeserializer<...>::ReadArithmetic<unsigned int>()
#2  node::sea::FindSingleExecutableResource()
#3  node::sea::FixupArgsForSEA(int, char**)
#4  node::Start(int, char**)

postject_find_resource("NODE_SEA_BLOB", &size, ...) returns NULL, then BlobDeserializer::ReadArithmetic calls memcpy(dst, NULL, sizeof(uint32_t)) → SIGSEGV.

Additional information

Suggested fix in node::sea::FindSingleExecutableBlob() (src/node_sea_bin.cc) — guard the deserialization on the resource lookup:

const char* blob = static_cast<const char*>(
    postject_find_resource("NODE_SEA_BLOB", &size, ...));
if (blob == nullptr) {
    fprintf(stderr,
            "node: SEA fuse is set but no NODE_SEA_BLOB resource was found "
            "in this binary. The host binary may be missing a PT_NOTE program "
            "header (run `readelf -lW <binary> | grep NOTE` to check).\n");
    exit(static_cast<int>(node::ExitCode::kGenericUserError));
}

Either that or CHECK_NOT_NULL(blob) — anything that surfaces a cause rather than a bare SEGV.

Related:

Linguagem predominante
JavaScript
Estrelas
122k
Forks
38.4k
Merge médio
3d 23h
PRs com merge (30d)
274

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