fix: memory leaks and input validation in i2c, spi, xxtea, and base modules

[Copilot]

Several malloc/calloc null-check additions in PR #123 introduced or exposed secondary issues: missing free on alternate return paths, a variable shadowing bug that silently zeroed the tx length, missing input validation allowing size_t underflow, and a NULL dereference via strtok.

Memory leaks on early-return paths

• luat_base.c / luat_cbcwait_cb: msg->ptr was not freed when sys_pub was not a function, leaking every queued callback allocation on that path.
• xxtea2.c / PUB_XxTEADecrypt: out_data was not freed and returned 0 (not NULL) when real_data_size > data_size.
• luat_lib_spi.c / l_spi_device_transfer: send_buff (heap-allocated when arg is a table) was not freed on the recv_length == 0 early return or on recv_buff allocation failure.

Variable shadowing causing silent data corruption

luat_lib_i2c.c / l_i2c_transfer: A const int tx_len was re-declared inside the table branch, shadowing the outer size_t tx_len. The outer variable remained 0, causing subsequent luat_i2c_transfer / i2c_soft_send calls to transmit 0 bytes.

// Before — shadows outer tx_len; outer stays 0
else if (lua_istable(L, 3)) {
    const int tx_len = lua_rawlen(L, 3);

// After — assigns to outer tx_len
else if (lua_istable(L, 3)) {
    tx_len = lua_rawlen(L, 3);

Missing input validation

• luat_lib_i2c.c / l_i2c_recv: A negative Lua integer passed as len would silently wrap to a huge size_t for malloc. Added len <= 0 guard with empty-string return.
• i2c_tools.c / i2c_tools: No minimum length check meant len - 8 / len - 9 could underflow as size_t. Added len < 9 early return. Also added a NULL check on the strtok result before passing it to memcmp.

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[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

Fixes memory leaks and hardens input validation across multiple low-level modules, addressing regressions/secondary issues introduced by earlier malloc/calloc NULL checks.

Changes:

• Free heap allocations on early-return/error paths in SPI transfer, base callback dispatch, and XXTEA decrypt.
• Fix I2C transfer variable shadowing that previously caused 0-length transmissions.
• Add input validation to prevent size_t underflow and NULL dereferences in I2C receive and i2c-tools.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
luat/modules/luat_lib_spi.c	Frees heap-allocated send buffer on additional early-return/error paths in SPI transfer.
luat/modules/luat_lib_i2c.c	Guards against non-positive recv lengths and fixes tx_len shadowing in I2C transfer.
luat/modules/luat_base.c	Frees queued callback allocation when sys_pub is not callable.
components/xxtea/src/xxtea2.c	Frees out_data and returns NULL on decrypt size mismatch.
components/i2c-tools/i2c_tools.c	Adds minimum length guard and checks strtok result before memcmp.

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