[PATCH] powerpc/kasan: fix shadow area set up for modules.

[PATCH] powerpc/kasan: fix shadow area set up for modules.

[Christophe Leroy]

When loading modules, from time to time an Oops is encountered
during the init of shadow area for globals. This is due to the
last page not always being mapped depending on the exact distance
between the start and the end of the shadow area and the alignment
with the page addresses.

Fix this by aligning the starting address with the page address.

Reported-by: Erhard F. <erhard_f@mailbox.org>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=204479
Fixes: 2edb16efc899 ("powerpc/32: Add KASAN support")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/mm/kasan/kasan_init_32.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
index 74f4555a62ba..99eac3fab83c 100644
--- a/arch/powerpc/mm/kasan/kasan_init_32.c
+++ b/arch/powerpc/mm/kasan/kasan_init_32.c
@@ -74,7 +74,7 @@ static int __ref kasan_init_region(void *start, size_t size)
 	if (!slab_is_available())
 		block = memblock_alloc(k_end - k_start, PAGE_SIZE);
 
-	for (k_cur = k_start; k_cur < k_end; k_cur += PAGE_SIZE) {
+	for (k_cur = k_start & PAGE_MASK; k_cur < k_end; k_cur += PAGE_SIZE) {
 		pmd_t *pmd = pmd_offset(pud_offset(pgd_offset_k(k_cur), k_cur), k_cur);
 		void *va = block ? block + k_cur - k_start : kasan_get_one_page();
 		pte_t pte = pfn_pte(PHYS_PFN(__pa(va)), PAGE_KERNEL);
-- 
2.13.3

Re: [PATCH] powerpc/kasan: fix shadow area set up for modules.

[Michael Ellerman]

On Fri, 2019-08-09 at 14:58:10 UTC, Christophe Leroy wrote:
> When loading modules, from time to time an Oops is encountered
> during the init of shadow area for globals. This is due to the
> last page not always being mapped depending on the exact distance
> between the start and the end of the shadow area and the alignment
> with the page addresses.
> 
> Fix this by aligning the starting address with the page address.
> 
> Reported-by: Erhard F. <erhard_f@mailbox.org>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=204479
> Fixes: 2edb16efc899 ("powerpc/32: Add KASAN support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/663c0c9496a69f80011205ba3194049bcafd681d

cheers