CVE-2026-87039 El manejador de la syscall i2s_configure pasa a los controladores un puntero a objeto del kernel provisto…
El verificador de syscalls de modo usuario z_vrfy_i2s_configure() en drivers/i2s/i2s_handlers.c copia la struct i2s_config del llamador desde memoria de usuario y, cuando cfg-frame_clk_freq es 0, salta directamente a z_impl_i2s_configure() sin realizar la verificación de propiedad y tipo K_SYSCALL_OBJ(config.mem_slab, K_OBJ_MEM_SLAB) ni la comprobación de block_size. En esa ruta, un puntero completamente no validado y elegido por el usuario llega al código del controlador, que está facultado para tratarlo como un…
CVSS 3.1
- Probabilidad de explotación · EPSS del 09/110,1 % · percentil 0
- Explotada activamenteNo confirmada
- Exploit públicoNo conocido
Afectados
zephyrproject zephyr
desde 4.4.0 hasta antes de 4.5.0
Qué hacer
- Verificá si usás zephyr y en qué versión.
- Actualizá a la versión corregida que indique el fabricante en su aviso o aplicá su mitigación.
- Revisá registros y accesos de los sistemas expuestos para descartar un uso previo.
Calculadora CVSS
CVSS 3.1 · 7.8 ALTA
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
- Vector de ataqueLocal
- Complejidad del ataqueAlta
- Privilegios requeridosBajos
- Interacción del usuarioNinguna
- AlcanceCambiado
- ConfidencialidadAlta
- IntegridadAlta
- DisponibilidadAlta
Descripción original
The user-mode syscall verifier z_vrfy_i2s_configure() in drivers/i2s/i2s_handlers.c copies the caller's struct i2s_config in from user memory and then, when cfg->frame_clk_freq is 0 (the API's "unconfigure the stream" request), jumps straight to z_impl_i2s_configure() without performing the K_SYSCALL_OBJ(config.mem_slab, K_OBJ_MEM_SLAB) ownership/type check or the block_size sanity check. The mem_slab field is a struct k_mem_slab *, so on that path a completely unvalidated, user-chosen pointer reaches driver code that is entitled to trust it as a real kernel object.
Any thread running under CONFIG_USERSPACE that has access to an I2S device object can trigger this with a single i2s_configure() call. Most in-tree drivers special-case frame_clk_freq == 0 and never store the caller's structure, but drivers/i2s/i2s_litex.c does not: i2s_litex_configure() only logs a warning for a mismatched frame clock, then memcpy()s the caller's config into stream->cfg and marks the stream I2S_STATE_READY. A subsequent i2s_trigger() with I2S_TRIGGER_START enables the FIFO interrupt, and the interrupt handlers i2s_litex_isr_rx() / i2s_litex_isr_tx() then call k_mem_slab_alloc() and k_mem_slab_free() on the attacker-supplied pointer in supervisor context.
The result is an arbitrary-pointer read/write primitive executed by the kernel on behalf of an unprivileged thread — k_mem_slab_alloc() takes a spinlock at slab->lock and reads and writes slab->free_list and the link word inside the returned "block" — which defeats the CONFIG_USERSPACE isolation boundary entirely. The same missing validation is a hazard for out-of-tree I2S drivers that retain the configuration on the unconfigure path. Builds without CONFIG_USERSPACE are unaffected, since the verifier is not used.
The fix zeroes config.mem_slab and config.block_size on the unconfigure path so the driver can never receive an unvalidated pointer, while still allowing a stream to be unconfigured by a caller that does not own a memory slab, as the API documents.
Referencias (2)
Resumen traducido automáticamente de la descripción original. Fuente: Nureq Monitor. Cómo funciona.