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From: tip-bot for Jiang Biao <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org,
	tglx@linutronix.de, jiang.biao2@zte.com.cn
Subject: [tip:x86/pti] x86/pti: Check the return value of pti_user_pagetable_walk_p4d()
Date: Thu, 19 Jul 2018 22:09:48 -0700	[thread overview]
Message-ID: <tip-b2b7d986a89b6c94b1331a909de1217214fb08c1@git.kernel.org> (raw)
In-Reply-To: <1532045192-49622-1-git-send-email-jiang.biao2@zte.com.cn>

Commit-ID:  b2b7d986a89b6c94b1331a909de1217214fb08c1
Gitweb:     https://git.kernel.org/tip/b2b7d986a89b6c94b1331a909de1217214fb08c1
Author:     Jiang Biao <jiang.biao2@zte.com.cn>
AuthorDate: Fri, 20 Jul 2018 08:06:31 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 20 Jul 2018 07:07:39 +0200

x86/pti: Check the return value of pti_user_pagetable_walk_p4d()

pti_user_pagetable_walk_p4d() can return NULL, so the return value should
be checked to prevent a NULL pointer dereference.

Add the check and a warning when the P4D 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/1532045192-49622-1-git-send-email-jiang.biao2@zte.com.cn

---
 arch/x86/mm/pti.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 7b1c85759005..001ee6b0619e 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -176,7 +176,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
 
 	if (pgd_none(*pgd)) {
 		unsigned long new_p4d_page = __get_free_page(gfp);
-		if (!new_p4d_page)
+		if (WARN_ON_ONCE(!new_p4d_page))
 			return NULL;
 
 		set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
@@ -195,9 +195,13 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
 static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
 {
 	gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
-	p4d_t *p4d = pti_user_pagetable_walk_p4d(address);
+	p4d_t *p4d;
 	pud_t *pud;
 
+	p4d = pti_user_pagetable_walk_p4d(address);
+	if (!p4d)
+		return NULL;
+
 	BUILD_BUG_ON(p4d_large(*p4d) != 0);
 	if (p4d_none(*p4d)) {
 		unsigned long new_pud_page = __get_free_page(gfp);
@@ -359,6 +363,9 @@ static void __init pti_clone_p4d(unsigned long addr)
 	pgd_t *kernel_pgd;
 
 	user_p4d = pti_user_pagetable_walk_p4d(addr);
+	if (!user_p4d)
+		return;
+
 	kernel_pgd = pgd_offset_k(addr);
 	kernel_p4d = p4d_offset(kernel_pgd, addr);
 	*user_p4d = *kernel_p4d;

      parent reply	other threads:[~2018-07-20  5:09 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-20  0:06 [PATCH v4 1/2] x86/pti: check the return value of pti_user_pagetable_walk_p4d Jiang Biao
2018-07-20  0:06 ` [PATCH v4 2/2] x86/pti: check the return value of pti_user_pagetable_walk_pmd Jiang Biao
2018-07-20  5:10   ` [tip:x86/pti] x86/pti: Check the return value of pti_user_pagetable_walk_pmd() tip-bot for Jiang Biao
2018-07-20  5:09 ` tip-bot for Jiang Biao [this message]

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