x86/pti: Check the return value of pti_user_pagetable_walk_pmd() (8c934e01) · Commits · 戴 / test

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.com.cn

arch/x86/mm/pti.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -205,7 +205,7 @@ 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_ONCE(!new_pud_page))
		return NULL;

		set_p4d(p4d, __p4d(_KERNPG_TABLE \| __pa(new_pud_page)));
		@@ -219,7 +219,7 @@ 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_ONCE(!new_pmd_page))
		return NULL;

		set_pud(pud, __pud(_KERNPG_TABLE \| __pa(new_pmd_page)));
		@@ -241,9 +241,13 @@ 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);
		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);

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