linux-kernel - [PATCH 03/26] bpfilter: reject kernel addresses

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Date:   Thu, 23 Jul 2020 08:08:45 +0200
From:   Christoph Hellwig <hch@....de>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        linux-sctp@...r.kernel.org, linux-hams@...r.kernel.org,
        linux-bluetooth@...r.kernel.org, bridge@...ts.linux-foundation.org,
        linux-can@...r.kernel.org, dccp@...r.kernel.org,
        linux-decnet-user@...ts.sourceforge.net,
        linux-wpan@...r.kernel.org, linux-s390@...r.kernel.org,
        mptcp@...ts.01.org, lvs-devel@...r.kernel.org,
        rds-devel@....oracle.com, linux-afs@...ts.infradead.org,
        tipc-discussion@...ts.sourceforge.net, linux-x25@...r.kernel.org
Subject: [PATCH 03/26] bpfilter: reject kernel addresses

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@....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