linux-kernel - [PATCH v2 2/2] x86/hyperv: add a bounds check to hv_cpu_number_to_vp

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Message-Id: <20201005233739.2560641-2-sashal@kernel.org>
Date:   Mon,  5 Oct 2020 19:37:39 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, vkuznets@...hat.com, mikelley@...rosoft.com,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH v2 2/2] x86/hyperv: add a bounds check to hv_cpu_number_to_vp_number()

We have code that calls into hv_cpu_number_to_vp_number() without
checking that the cpu number is valid, which would cause
hv_cpu_number_to_vp_number() to dereference invalid memory.

Instead, have hv_cpu_number_to_vp_number() fail gracefully and add a
warning to make sure we catch these issues quickly.

Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/asm-generic/mshyperv.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index c5edc5e08b94f..c7d22cb8340ff 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -125,6 +125,9 @@ extern u32 hv_max_vp_index;
  */
 static inline int hv_cpu_number_to_vp_number(int cpu_number)
 {
+	if (WARN_ON_ONCE(cpu_number < 0 || cpu_number >= num_possible_cpus()))
+		return VP_INVAL;
+
 	return hv_vp_index[cpu_number];
 }
 
-- 
2.25.1