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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Juergen Gross <jgross@suse.com>, Sasha Levin <sashal@kernel.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	xen-devel@lists.xenproject.org
Subject: [Xen-devel] [PATCH AUTOSEL 4.4 057/174] xen, cpu_hotplug: Prevent an out of bounds access
Date: Thu, 16 Jan 2020 12:40:54 -0500
Message-ID: <20200116174251.24326-57-sashal@kernel.org> (raw)
In-Reply-To: <20200116174251.24326-1-sashal@kernel.org>

From: Dan Carpenter <dan.carpenter@oracle.com>

[ Upstream commit 201676095dda7e5b31a5e1d116d10fc22985075e ]

The "cpu" variable comes from the sscanf() so Smatch marks it as
untrusted data.  We can't pass a higher value than "nr_cpu_ids" to
cpu_possible() or it results in an out of bounds access.

Fixes: d68d82afd4c8 ("xen: implement CPU hotplugging")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/xen/cpu_hotplug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
index f4e59c445964..17054d695411 100644
--- a/drivers/xen/cpu_hotplug.c
+++ b/drivers/xen/cpu_hotplug.c
@@ -53,7 +53,7 @@ static int vcpu_online(unsigned int cpu)
 }
 static void vcpu_hotplug(unsigned int cpu)
 {
-	if (!cpu_possible(cpu))
+	if (cpu >= nr_cpu_ids || !cpu_possible(cpu))
 		return;
 
 	switch (vcpu_online(cpu)) {
-- 
2.20.1


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