The Linux kernel's kho_preserved_memory_reserve() function calculates preservation size by shifting a 32-bit integer, limiting correct operation to preservations up to 2 GiB. Larger preservations, which can be created via kho_preserve_pages() such as memblock reserve_mem, trigger undefined behavior due to integer overflow in the size calculation. The fix replaces the 32-bit integer with a 64-bit unsigned long (1UL) to correctly handle larger preservation sizes.

Incorrect size calculation for memory preservations larger than 2 GiB can cause undefined behavior in the kernel's memory reservation logic. This could potentially affect system stability or memory management correctness when large memory reservations are used.

A fix is available that corrects the size calculation by using a 64-bit integer shift. Users should apply the official Linux kernel patch that updates kho_preserved_memory_reserve() to use 1UL for shifting. No additional mitigation is indicated.