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Commit 16939943 authored by Jiang Biao's avatar Jiang Biao Committed by Greg Kroah-Hartman
Browse files

x86/pti: Check the return value of pti_user_pagetable_walk_pmd() 



[ 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: default avatarJiang Biao <jiang.biao2@zte.com.cn>
Signed-off-by: default avatarThomas 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.com.cn


Signed-off-by: default avatarSasha Levin <alexander.levin@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 36d6a43a

arch/x86/mm/pti.c

+7 −3
Original line number Diff line number Diff line
@@ -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);