[PATCH 1/5] x86/pti: check the return value of pti_user_pagetable_walk_p4d
From: Jiang Biao
Date: Mon Jul 16 2018 - 00:22:23 EST
pti_user_pagetable_walk_p4d() may return NULL, we should check the
return value to avoid NULL pointer dereference.
Signed-off-by: Jiang Biao <jiang.biao2@xxxxxxxxxx>
---
arch/x86/mm/pti.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 4d418e7..be9e5bc 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -195,8 +195,10 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
{
gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
- p4d_t *p4d = pti_user_pagetable_walk_p4d(address);
pud_t *pud;
+ p4d_t *p4d = pti_user_pagetable_walk_p4d(address);
+ if (WARN_ON(!p4d))
+ return NULL;
BUILD_BUG_ON(p4d_large(*p4d) != 0);
if (p4d_none(*p4d)) {
@@ -354,6 +356,9 @@ static void __init pti_clone_p4d(unsigned long addr)
pgd_t *kernel_pgd;
user_p4d = pti_user_pagetable_walk_p4d(addr);
+ if (WARN_ON(!user_p4d))
+ return;
+
kernel_pgd = pgd_offset_k(addr);
kernel_p4d = p4d_offset(kernel_pgd, addr);
*user_p4d = *kernel_p4d;
--
2.7.4