[PATCH] mm: kasan: Index page hierarchy as an array
Linus Walleij
linus.walleij at linaro.org
Fri Nov 6 03:51:57 EST 2020
When freeing page directories, KASan was consistently
indexing through the page hierarchy like this:
static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d) {
pud_t *pud;
int i;
for (i = 0; i < PTRS_PER_PUD; i++) {
pud = pud_start + i;
if (!pud_none(*pud))
if (!pud_none(pud_start[i]))
return;
}
}
That is: implicitly add i sizeof(put_t) idices to
the variable pud.
On ARM32 arch/arm/include/asm/pgtable-2level.h has folded
the PMDs into the PUDs and thus has this definition of
pud_none():
#define pud_none(pud) (0)
This will make the above construction emit this harmless
build warning on ARM32:
mm/kasan/init.c: In function 'kasan_free_pud':
>> mm/kasan/init.c:318:9: warning: variable 'pud' set but not used [-Wunused-but-set-variable]
318 | pud_t *pud;
| ^~~
Using an explicit array removes this problem and also makes
the build warning go away. Arguably the code also gets
easier to read.
So I fixed all the kasan_free_p??() to use explicit
array inidices instead.
Fixes: 421015713b30 ("ARM: 9017/2: Enable KASan for ARM")
Reported-by: kernel test robot <lkp at intel.com>
Suggested-by: Ard Biesheuvel <ardb at kernel.org>
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
mm/kasan/init.c | 16 ++++------------
1 file changed, 4 insertions(+), 12 deletions(-)
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index fe6be0be1f76..3c74c30996ef 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -285,12 +285,10 @@ int __ref kasan_populate_early_shadow(const void *shadow_start,
static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
{
- pte_t *pte;
int i;
for (i = 0; i < PTRS_PER_PTE; i++) {
- pte = pte_start + i;
- if (!pte_none(*pte))
+ if (!pte_none(pte_start[i]))
return;
}
@@ -300,12 +298,10 @@ static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
{
- pmd_t *pmd;
int i;
for (i = 0; i < PTRS_PER_PMD; i++) {
- pmd = pmd_start + i;
- if (!pmd_none(*pmd))
+ if (!pmd_none(pmd_start[i]))
return;
}
@@ -315,12 +311,10 @@ static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
{
- pud_t *pud;
int i;
for (i = 0; i < PTRS_PER_PUD; i++) {
- pud = pud_start + i;
- if (!pud_none(*pud))
+ if (!pud_none(pud_start[i]))
return;
}
@@ -330,12 +324,10 @@ static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
{
- p4d_t *p4d;
int i;
for (i = 0; i < PTRS_PER_P4D; i++) {
- p4d = p4d_start + i;
- if (!p4d_none(*p4d))
+ if (!p4d_none(p4d_start[i]))
return;
}
--
2.26.2
More information about the linux-arm-kernel
mailing list