CVE-2026-74524

In the Linux kernel, the following vulnerability has been resolved:

riscv: mm: Fix out-of-bounds page-table walk during memory hot-remove

removepudmapping() and removep4dmapping() obtain a child table base with pudoffset(p4dp, 0) and p4doffset(pgd, 0), then add the index for addr.

RISC-V folds page-table levels at runtime. When a level is folded, its offset helper returns the parent entry itself, but the index can still be nonzero. Adding it walks past the parent table. Sv48 folds P4D, while Sv39 folds both P4D and PUD, so memory hot-remove can descend into unrelated memory and pass an invalid page to _freepages(). This can trigger:

kernel BUG at include/linux/mm.h:1810! VMBUGONPAGE(pagerefcount(page) == 0) archremovememory+0x1e/0x5c tryremovememory+0x15e/0x200 removememory+0x24/0x3c

Only add the index when the corresponding page-table level is enabled, matching p4doffset() and pudoffset().