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[PATCH 03/26] bpfilter: reject kernel addresses

To: "David S. Miller" <davem@xxxxxxxxxxxxx>, Jakub Kicinski <kuba@xxxxxxxxxx>, Alexei Starovoitov <ast@xxxxxxxxxx>, Daniel Borkmann <daniel@xxxxxxxxxxxxx>, Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>, Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>, Eric Dumazet <edumazet@xxxxxxxxxx>
Subject: [PATCH 03/26] bpfilter: reject kernel addresses
Cc: linux-crypto@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, bpf@xxxxxxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxx, coreteam@xxxxxxxxxxxxx, linux-sctp@xxxxxxxxxxxxxxx, linux-hams@xxxxxxxxxxxxxxx, linux-bluetooth@xxxxxxxxxxxxxxx, bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx, linux-can@xxxxxxxxxxxxxxx, dccp@xxxxxxxxxxxxxxx, linux-decnet-user@xxxxxxxxxxxxxxxxxxxxx, linux-wpan@xxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, mptcp@xxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, rds-devel@xxxxxxxxxxxxxx, linux-afs@xxxxxxxxxxxxxxxxxxx, tipc-discussion@xxxxxxxxxxxxxxxxxxxxx, linux-x25@xxxxxxxxxxxxxxx
From: Christoph Hellwig <hch@xxxxxx>
Date: Thu, 23 Jul 2020 08:08:45 +0200
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@xxxxxx>
---
 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


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