CVE-2023-52730

What it actually does

Resource leaks occur in error paths of sdio_add_func() and sdio_init_func() because sdio_func_present() gates only device_del() while of_node_put() and put_device() calls are skipped, and unbalanced get_device/put_device calls on card->dev allow unreleased allocations from mmc_alloc_card and sdio_alloc_func.

Why it matters to the business

Repeated SDIO attachment failures on affected Linux kernels can slowly exhaust kernel memory, increasing risk of instability or denial of service in systems that rely on MMC/SDIO hardware, especially under fault conditions or frequent card insertion.

How an attack unfolds

An attacker or test harness induces failures during mmc_rescan or mmc_attach_sdio by triggering error returns from sdio_add_func or sdio_init_func; the missing cleanup leaves kmalloc-allocated sdio_func objects and device references unreleased, accumulating over repeated attempts.

How to fix it

Apply the upstream fix in commit 92ff03c2563c9b57a027c744750f3b7d2f261c58 which moves get_device to sdio_alloc_func, ensures of_node_put and put_device are always called, and limits sdio_func_present to device_del only; rebuild and deploy the updated kernel.

How to confirm the fix worked

Confirm the fix commit is present in the running kernel tree; run fault-injection tests that previously produced kmemleak reports for mmc_alloc_card and sdio_alloc_func and verify no leaks remain.

Typical attack path

1. Initiate MMC/SDIO rescan or card attachment
2. Force error return from sdio_add_func or sdio_init_func
3. Bypass of_node_put and put_device in the failure path
4. Accumulate unreferenced kernel memory objects

How to detect it

Inspect dmesg, kmemleak, or kernel log buffers for unreferenced objects with backtraces containing mmc_alloc_card, sdio_alloc_func, mmc_attach_sdio, or mmc_rescan after SDIO errors.

What your security team should do

• Upgrade to a kernel containing commit 92ff03c2563c9b57a027c744750f3b7d2f261c58
• Enable kmemleak or similar memory debugging on SDIO-enabled systems
• Prioritize patching on devices with frequent SDIO card activity
• Monitor for memory pressure correlated with mmc_rescan activity