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CVE-2026-90338

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Opublikowano: Przetłumaczono: NVD NIST

Streszczenie

W jądrze Linux występuje podatność w sterowniku konsoli szeregowej amba-pl011. Funkcja pl011_console_write_atomic() wywoływana w kontekście atomowym (nbcon) używa clk_enable(), które w jądrze z PREEMPT_RT może zasnąć, co prowadzi do błędu "sleeping function called from invalid context". Problem dotyczy urządzeń arm32 i arm64 z Device Tree, gdzie UART korzysta z zegara zarządzanego przez common-clk.

Ocena ryzyka

Na systemach z PREEMPT_RT wywołanie printk w kontekście atomowym (np. z NMI) może wywołać błąd jądra i zawieszenie systemu. Dodatkowo możliwe jest niebezpieczne pozyskanie blokady enable_lock z kontekstu NMI.

Rekomendacja

Zaktualizuj jądro Linux do wersji zawierającej poprawkę, która przenosi włączanie zegara do pl011_console_setup() i zwalnia go w .exit() konsoli. Jeśli aktualizacja nie jest możliwa, unikaj konfiguracji PREEMPT_RT z konsolą pl011 lub ogranicz wywołania printk z kontekstu atomowego.

Inne podatności w Linux kernel

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Oryginalny opis (angielski, źródło NVD)

In the Linux kernel, the following vulnerability has been resolved: serial: amba-pl011: keep console clock enabled for atomic writes pl011_console_write_atomic() runs from nbcon atomic context, where sleeping is not allowed. It calls clk_enable(), which takes the common-clk enable_lock. Under PREEMPT_RT that is a sleeping lock: clk_enable_lock() first tries spin_trylock_irqsave(), but on contention falls back to spin_lock_irqsave(). Therefore, an atomic-context printk on an RT kernel with a clk-backed pl011 can trip: BUG: sleeping function called from invalid context at spinlock_rt.c:48 __might_resched from rt_spin_lock rt_spin_lock from clk_enable_lock clk_enable_lock from clk_enable clk_enable from pl011_console_write_atomic ... from vprintk_emit This was found and reproduced on PREEMPT_RT. Arm32 and arm64 DT SoCs are affected; arm64 SBSA/ACPI has no clk, so clk_enable(NULL) short-circuits before the lock. In addition, write_atomic() may be invoked from NMI context and is documented to avoid locking. Removing clk_enable() from the callback also avoids a potentially unsafe NMI acquisition of the common-clock enable_lock. An nbcon atomic-capable console must be printable from any context, so the clock cannot be gated between writes. Enable the clock while the console is available for output: use clk_prepare_enable() in pl011_console_setup(), release it via clk_disable_unprepare() in the console .exit() callback, and drop the per-write clk_enable()/clk_disable() pairs from write_atomic() and write_thread(). When printk suspends consoles, drop the reference after uart_suspend_port() stops console access and restore it before uart_resume_port() -- but only if suspend actually marked the port suspended (a wake-capable tty stays running and must keep its clock), and keep it when console_suspend_enabled is false so no_console_suspend works. The active power cost of keeping the clock enabled is platform-dependent: none where the UART clock is a fixed always-on oscillator, real where it is a gateable clock branch, which then cannot be gated (nor possibly can its parent clocks) while the console is available for output. When serial core actually suspends the port, the reference is released so the clock provider can gate the clock tree.

Dane podatności pochodzą z NVD (NIST) · CISA KEV · EPSS