Undefined Behavior in Linux Kernel's AMD Graphics Driver due to Shift Issue

CVE-2021-4460

What is CVE-2021-4460?

A vulnerability has been identified in the Linux kernel's AMD graphics driver related to shift operations. When the functions get_num_sdma_queues or get_num_xgmi_sdma_queues return zero, it triggers a shift operation where the shift amount exceeds the number of bits in the operand, resulting in undefined behavior. This issue can potentially lead to system instability. The resolution involves setting num_sdma_queues or num_xgmi_sdma_queues to ULLONG_MAX when the count is equal to or exceeds the operand's bit count, addressing the warning raised by Undefined Behavior Sanitizer (UBSAN).

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