Check the return value of pti_user_pagetable_walk_pmd() to avoid NULL pointer dereference. And add warning for fail allocation.
Signed-off-by: Jiang Biao <jiang.bi...@zte.com.cn> --- arch/x86/mm/pti.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 7c402e9..3dba6a7 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -203,7 +203,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) BUILD_BUG_ON(p4d_large(*p4d) != 0); if (p4d_none(*p4d)) { unsigned long new_pud_page = __get_free_page(gfp); - if (!new_pud_page) + if (WARN_ON(!new_pud_page)) return NULL; set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page))); @@ -217,7 +217,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) } if (pud_none(*pud)) { unsigned long new_pmd_page = __get_free_page(gfp); - if (!new_pmd_page) + if (WARN_ON(!new_pmd_page)) return NULL; set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page))); @@ -239,8 +239,10 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address) { gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); - pmd_t *pmd = pti_user_pagetable_walk_pmd(address); pte_t *pte; + pmd_t *pmd = pti_user_pagetable_walk_pmd(address); + if (!pmd) + return NULL; /* We can't do anything sensible if we hit a large mapping. */ if (pmd_large(*pmd)) { -- 2.7.4