Linux Kernel Clock Management Vulnerability in SpacemiT K1 SoC

A vulnerability in the Linux kernel's clock management for the SpacemiT K1 system-on-chip (SoC) has been addressed. The issue arose because the pll1_d8 clock, essential for various other clocks including those used by the APB and AXI buses, was inadvertently disabled. This occurred while the system was handling a probe deferral response when requesting a reset controller. The CLK_DMA clock, along with its parent clocks, had already been activated. However, in response to the probe deferral, the CLK_DMA clock was turned off, which caused a cascading effect that reduced the enable count of parent clocks, including pll1_d8. Once the enable count for pll1_d8 reached zero, it was disabled, leading to a system hang. The vulnerability has been fixed by marking the pll1_d8 clock as critical, preventing it from being disabled during such probe deferral responses. Additionally, a new macro has been defined to allow the inclusion of clock flags for certain types of clocks.

Impact

The original vulnerability could lead to a system hang by improperly managing clock states, particularly for the pll1_d8 clock on the SpacemiT K1 SoC.