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From:   Ilya Matveychikov <matvejchikov@gmail.com>
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Subject: [PATCH] ksys_mount: check for permissions before resource allocation
Message-Id: <D2317950-0DB0-4311-ADB1-FF677B676E04@gmail.com>
Date:   Tue, 5 Jun 2018 06:00:47 +0400
To:     linux-kernel@vger.kernel.org
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Early check for mount permissions prevents possible allocation of 3
pages from kmalloc() pool by unpriveledged user which can be used for
spraying the kernel heap.

Signed-off-by: Ilya V. Matveychikov <matvejchikov@gmail.com>
---
 fs/namespace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/namespace.c b/fs/namespace.c
index 5f75969adff1..1ef8feb2de2a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3046,6 +3046,9 @@ int ksys_mount(char __user *dev_name, char __user =
*dir_name, char __user *type,
 	char *kernel_dev;
 	void *options;

+	if (!may_mount())
+		return -EPERM;
+
 	kernel_type =3D copy_mount_string(type);
 	ret =3D PTR_ERR(kernel_type);
 	if (IS_ERR(kernel_type))
--
2.17.0