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From:   Christoph Hellwig <hch@lst.de>
To:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
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        Eric Dumazet <edumazet@google.com>
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        netdev@vger.kernel.org, bpf@vger.kernel.org,
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Subject: [PATCH 03/26] bpfilter: reject kernel addresses
Date:   Thu, 23 Jul 2020 08:08:45 +0200
Message-Id: <20200723060908.50081-4-hch@lst.de>
In-Reply-To: <20200723060908.50081-1-hch@lst.de>
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The bpfilter user mode helper processes the optval address using
process_vm_readv.  Don't send it kernel addresses fed under
set_fs(KERNEL_DS) as that won't work.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 net/bpfilter/bpfilter_kern.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
index 78d561f2c54da7..00540457e5f4d3 100644
--- a/net/bpfilter/bpfilter_kern.c
+++ b/net/bpfilter/bpfilter_kern.c
@@ -70,6 +70,10 @@ static int bpfilter_process_sockopt(struct sock *sk, int optname,
 		.addr		= (uintptr_t)optval,
 		.len		= optlen,
 	};
+	if (uaccess_kernel()) {
+		pr_err("kernel access not supported\n");
+		return -EFAULT;
+	}
 	return bpfilter_send_req(&req);
 }
 
-- 
2.27.0