Commit 5cb86245 authored Jan 23, 2021 by Lecopzer Chen Committed by Greg Kroah-Hartman Jan 27, 2021

kasan: fix unaligned address is unhandled in kasan_remove_zero_shadow

commit a11a496ee6e2ab6ed850233c96b94caf042af0b9 upstream.

During testing kasan_populate_early_shadow and kasan_remove_zero_shadow,
if the shadow start and end address in kasan_remove_zero_shadow() is not
aligned to PMD_SIZE, the remain unaligned PTE won't be removed.

In the test case for kasan_remove_zero_shadow():

    shadow_start: 0xffffffb802000000, shadow end: 0xffffffbfbe000000

    3-level page table:
      PUD_SIZE: 0x40000000 PMD_SIZE: 0x200000 PAGE_SIZE: 4K

0xffffffbf80000000 ~ 0xffffffbfbdf80000 will not be removed because in
kasan_remove_pud_table(), kasan_pmd_table(*pud) is true but the next
address is 0xffffffbfbdf80000 which is not aligned to PUD_SIZE.

In the correct condition, this should fallback to the next level
kasan_remove_pmd_table() but the condition flow always continue to skip
the unaligned part.

Fix by correcting the condition when next and addr are neither aligned.

Link: https://lkml.kernel.org/r/20210103135621.83129-1-lecopzer@gmail.com


Fixes: 0207df4f ("kernel/memremap, kasan: make ZONE_DEVICE with work with KASAN")
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: YJ Chiang <yj.chiang@mediatek.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 66fb76f3

mm/kasan/kasan_init.c

+12 −8

Original line number	Diff line number	Diff line
		@@ -372,10 +372,11 @@ static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,

		if (kasan_pte_table(*pmd)) {
		if (IS_ALIGNED(addr, PMD_SIZE) &&
		IS_ALIGNED(next, PMD_SIZE))
		IS_ALIGNED(next, PMD_SIZE)) {
		pmd_clear(pmd);
		continue;
		}
		}
		pte = pte_offset_kernel(pmd, addr);
		kasan_remove_pte_table(pte, addr, next);
		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
		@@ -397,10 +398,11 @@ static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,

		if (kasan_pmd_table(*pud)) {
		if (IS_ALIGNED(addr, PUD_SIZE) &&
		IS_ALIGNED(next, PUD_SIZE))
		IS_ALIGNED(next, PUD_SIZE)) {
		pud_clear(pud);
		continue;
		}
		}
		pmd = pmd_offset(pud, addr);
		pmd_base = pmd_offset(pud, 0);
		kasan_remove_pmd_table(pmd, addr, next);
		@@ -423,10 +425,11 @@ static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,

		if (kasan_pud_table(*p4d)) {
		if (IS_ALIGNED(addr, P4D_SIZE) &&
		IS_ALIGNED(next, P4D_SIZE))
		IS_ALIGNED(next, P4D_SIZE)) {
		p4d_clear(p4d);
		continue;
		}
		}
		pud = pud_offset(p4d, addr);
		kasan_remove_pud_table(pud, addr, next);
		kasan_free_pud(pud_offset(p4d, 0), p4d);
		@@ -457,10 +460,11 @@ void kasan_remove_zero_shadow(void *start, unsigned long size)

		if (kasan_p4d_table(*pgd)) {
		if (IS_ALIGNED(addr, PGDIR_SIZE) &&
		IS_ALIGNED(next, PGDIR_SIZE))
		IS_ALIGNED(next, PGDIR_SIZE)) {
		pgd_clear(pgd);
		continue;
		}
		}

		p4d = p4d_offset(pgd, addr);
		kasan_remove_p4d_table(p4d, addr, next);