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From:   Kangjie Lu <kjlu@umn.edu>
To:     kjlu@umn.edu
Cc:     pakki001@umn.edu, "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Sasha Levin <sashal@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] hyperv: a potential NULL pointer dereference
Date:   Thu, 14 Mar 2019 00:46:51 -0500
Message-Id: <20190314054651.1315-1-kjlu@umn.edu>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In case alloc_page, the fix returns -ENOMEM to avoid the potential
NULL pointer dereference.

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
---
 arch/x86/hyperv/hv_init.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 7abb09e2eeb8..dfdb4ce1ae9c 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -102,9 +102,13 @@ static int hv_cpu_init(unsigned int cpu)
 	u64 msr_vp_index;
 	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
 	void **input_arg;
+	struct page *pg;
 
 	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
-	*input_arg = page_address(alloc_page(GFP_KERNEL));
+	pg = alloc_page(GFP_KERNEL);
+	if (unlikely(!pg))
+		return -ENOMEM;
+	*input_arg = page_address(pg);
 
 	hv_get_vp_index(msr_vp_index);
 
-- 
2.17.1