kasan: fix unaligned address is unhandled in kasan_remove_zero_shadow

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.

Fixes 0207df4fa1a86 ("kernel/memremap, kasan: make ZONE_DEVICE with work with KASAN")

Signed-off-by Lecopzer Chen <[email protected]>

---
 mm/kasan/init.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

mm/kasan/init.c +12 -9

index 67051cfae41c..ae9158f7501f 100644
@@ -372,9 +372,10 @@ 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;
+                               continue;
+                       }
                }
                pte = pte_offset_kernel(pmd, addr);
                kasan_remove_pte_table(pte, addr, next);

@@ -397,9 +398,10 @@ 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;
+                               continue;
+                       }
                }
                pmd = pmd_offset(pud, addr);
                pmd_base = pmd_offset(pud, 0);

@@ -423,9 +425,10 @@ 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;
+                               continue;
+                       }
                }
                pud = pud_offset(p4d, addr);
                kasan_remove_pud_table(pud, addr, next);

@@ -456,9 +459,10 @@ 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;
+                               continue;
+                       }
                }
 
                p4d = p4d_offset(pgd, addr);
--

2.25.1