Commit 61ef8dda authored by Ryan Roberts's avatar Ryan Roberts Committed by Will Deacon
Browse files

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



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: default avatarAnshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Tested-by: default avatarLuiz Capitulino <luizcap@redhat.com>
Link: https://lore.kernel.org/r/20250422081822.1836315-8-ryan.roberts@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent f89b399e

mm/vmalloc.c

+6 −2
Original line number Diff line number Diff line
@@ -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);