From: Jiang Biao jiang.biao2@zte.com.cn
[ Upstream commit 8c934e01a7ce685d98e970880f5941d79272c654 ]
pti_user_pagetable_walk_pmd() can return NULL, so the return value should be checked to prevent a NULL pointer dereference.
Add the check and a warning when the PMD allocation fails.
Signed-off-by: Jiang Biao jiang.biao2@zte.com.cn Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: dave.hansen@linux.intel.com Cc: luto@kernel.org Cc: hpa@zytor.com Cc: albcamus@gmail.com Cc: zhong.weidong@zte.com.cn Link: https://lkml.kernel.org/r/1532045192-49622-2-git-send-email-jiang.biao2@zte.... Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- arch/x86/mm/pti.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 63afd15b32a5..7786ab306225 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -191,7 +191,7 @@ static __init 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_ONCE(!new_pud_page)) return NULL;
set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page))); @@ -205,7 +205,7 @@ static __init 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_ONCE(!new_pmd_page)) return NULL;
set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page))); @@ -227,9 +227,13 @@ static __init 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); + pmd_t *pmd; pte_t *pte;
+ 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)) { WARN_ON(1);