From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Sasha Levin To: "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: Jiang Biao , Thomas Gleixner , "dave.hansen@linux.intel.com" , "luto@kernel.org" , "hpa@zytor.com" , "albcamus@gmail.com" , "zhong.weidong@zte.com.cn" , Sasha Levin Subject: [PATCH AUTOSEL 4.14 66/67] x86/pti: Check the return value of pti_user_pagetable_walk_pmd() Date: Fri, 7 Sep 2018 00:38:08 +0000 Message-ID: <20180907003716.57737-66-alexander.levin@microsoft.com> References: <20180907003716.57737-1-alexander.levin@microsoft.com> In-Reply-To: <20180907003716.57737-1-alexander.levin@microsoft.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: From: Jiang Biao [ 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 Signed-off-by: Thomas Gleixner 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.bia= o2@zte.com.cn Signed-off-by: Sasha Levin --- 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(unsign= ed long address) BUILD_BUG_ON(p4d_large(*p4d) !=3D 0); if (p4d_none(*p4d)) { unsigned long new_pud_page =3D __get_free_page(gfp); - if (!new_pud_page) + if (WARN_ON_ONCE(!new_pud_page)) return NULL; =20 set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page))); @@ -205,7 +205,7 @@ static __init pmd_t *pti_user_pagetable_walk_pmd(unsign= ed long address) } if (pud_none(*pud)) { unsigned long new_pmd_page =3D __get_free_page(gfp); - if (!new_pmd_page) + if (WARN_ON_ONCE(!new_pmd_page)) return NULL; =20 set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page))); @@ -227,9 +227,13 @@ static __init pmd_t *pti_user_pagetable_walk_pmd(unsig= ned long address) static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address) { gfp_t gfp =3D (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); - pmd_t *pmd =3D pti_user_pagetable_walk_pmd(address); + pmd_t *pmd; pte_t *pte; =20 + pmd =3D 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); --=20 2.17.1