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mm/vmalloc: Warn on improper use of vunmap_range()

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A call to vmalloc_huge() may cause memory blocks to be mapped at pmd or
pud level. But it is possible to subsequently call vunmap_range() on a
sub-range of the mapped memory, which partially overlaps a pmd or pud.
In this case, vmalloc unmaps the entire pmd or pud so that the
no-overlapping portion is also unmapped. Clearly that would have a bad
outcome, but it's not something that any callers do today as far as I
can tell. So I guess it's just expected that callers will not do this.

However, it would be useful to know if this happened in future; let's
add a warning to cover the eventuality.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Tested-by: Luiz Capitulino <luizcap@redhat.com>
Link: https://lore.kernel.org/r/20250422081822.1836315-8-ryan.roberts@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Ryan Roberts
2025-04-22 09:18:15 +01:00
committed by Will Deacon
parent f89b399e8d
commit 61ef8ddaa3
1 changed files with 6 additions and 2 deletions
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8
mm/vmalloc.c
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@@ -374,8 +374,10 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
if (cleared || pmd_bad(*pmd))
*mask |= PGTBL_PMD_MODIFIED;
if (cleared)
if (cleared) {
WARN_ON(next - addr < PMD_SIZE);
continue;
}
if (pmd_none_or_clear_bad(pmd))
continue;
vunmap_pte_range(pmd, addr, next, mask);
@@ -399,8 +401,10 @@ static void vunmap_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
if (cleared || pud_bad(*pud))
*mask |= PGTBL_PUD_MODIFIED;
if (cleared)
if (cleared) {
WARN_ON(next - addr < PUD_SIZE);
continue;
}
if (pud_none_or_clear_bad(pud))
continue;
vunmap_pmd_range(pud, addr, next, mask);