Left Shift Underflow Vulnerability in Linux Kernel Affecting QEMU NVMe Devices

CVE-2025-40295

What is CVE-2025-40295?

This vulnerability resides in the Linux kernel where a left shift underflow occurs when the block size of an inode exceeds the size of a memory page during interactions with QEMU NVMe devices. Specifically, if both the logical and physical block sizes are elevated to 8 KiB, the system experiences an error when attempting to read the partition table at boot, triggering a UBSAN warning. The critical condition arises due to inode values being misconfigured, particularly when CONFIG_TRANSPARENT_HUGEPAGE is enabled, allowing inode block size values that can lead to erroneous data manipulations. This issue primarily affects block devices while leaving file input/output operations less prone to the issue due to preventive measures in place.

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