mirrors/linux
2
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2026-08-31 15:22:21 -04:00
Code Issues Packages Projects Releases Wiki Activity

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

Browse Source 
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().

Fixes: c75a74f4ba ("riscv: mm: Add memory hotplugging support")
Assisted-by: Claude:claude-fable-5
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Link: https://patch.msgid.link/20260729012132.24882-1-kmehltretter@gmail.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>
This commit is contained in:
Karl Mehltretter
2026-07-29 03:21:32 +02:00
committed by Paul Walmsley
parent f51fed61ee
commit a0188cc133
1 changed files with 2 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
arch/riscv/mm/init.c
View File

@@ -1625,7 +1625,7 @@ static void __meminit remove_pud_mapping(pud_t *pud_base, unsigned long addr, un
for (; addr < end; addr = next) {
next = pud_addr_end(addr, end);
pudp = pud_base + pud_index(addr);
pudp = pgtable_l4_enabled ? pud_base + pud_index(addr) : pud_base;
pud = pudp_get(pudp);
if (!pud_present(pud))
continue;
@@ -1656,7 +1656,7 @@ static void __meminit remove_p4d_mapping(p4d_t *p4d_base, unsigned long addr, un
for (; addr < end; addr = next) {
next = p4d_addr_end(addr, end);
p4dp = p4d_base + p4d_index(addr);
p4dp = pgtable_l5_enabled ? p4d_base + p4d_index(addr) : p4d_base;
p4d = p4dp_get(p4dp);
if (!p4d_present(p4d))
continue;