When feeding addresses to userspace we can't support kernel addresses
that were fed under set_fs(KERNEL_DS) from bpf-cgroup.

Signed-off-by: Christoph Hellwig <hch(a)lst.de>
---
 net/bpfilter/bpfilter_kern.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
index 2c31e82cb953af..977e9dad72ca4f 100644
--- a/net/bpfilter/bpfilter_kern.c
+++ b/net/bpfilter/bpfilter_kern.c
@@ -41,6 +41,11 @@ static int __bpfilter_process_sockopt(struct sock *sk, int optname,
 	ssize_t n;
 	int ret = -EFAULT;
 
+	if (uaccess_kernel()) {
+		pr_err("kernel access not supported\n");
+		return -EFAULT;
+	}
+
 	req.is_set = is_set;
 	req.pid = current->pid;
 	req.cmd = optname;
-- 
2.27.0