Bug 2517005 (CVE-2026-74524)

Summary: CVE-2026-74524 kernel: riscv: mm: Fix out-of-bounds page-table walk during memory hot-remove
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel. When performing memory hot-remove operations on systems using RISC-V architecture, an out-of-bounds page-table walk can occur. This issue arises because the system attempts to access memory outside of its designated boundaries, potentially leading to a kernel bug and a system crash. This vulnerability could allow a local attacker to cause a denial of service.
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Description OSIDB Bzimport 2026-08-15 12:44:21 UTC 
In the Linux kernel, the following vulnerability has been resolved:

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

remove_pud_mapping() and remove_p4d_mapping() obtain a child table base
with pud_offset(p4dp, 0) and p4d_offset(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 __free_pages(). This can trigger:

  kernel BUG at include/linux/mm.h:1810!
  VM_BUG_ON_PAGE(page_ref_count(page) == 0)
  arch_remove_memory+0x1e/0x5c
  try_remove_memory+0x15e/0x200
  remove_memory+0x24/0x3c

Only add the index when the corresponding page-table level is enabled,
matching p4d_offset() and pud_offset().
Comment 1 gkamathe 2026-08-21 11:51:44 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081545-CVE-2026-74524-308e@gregkh/T