openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 117 insertions, 0 deletions

diff --git a/net/ipv4/fou_bpf.c b/net/ipv4/fou_bpf.c
new file mode 100644
index 000000000..54984f317
--- /dev/null
+++ b/net/ipv4/fou_bpf.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Unstable Fou Helpers for TC-BPF hook
+ *
+ * These are called from SCHED_CLS BPF programs. Note that it is
+ * allowed to break compatibility for these functions since the interface they
+ * are exposed through to BPF programs is explicitly unstable.
+ */
+
+#include <linux/bpf.h>
+#include <linux/btf_ids.h>
+
+#include <net/dst_metadata.h>
+#include <net/fou.h>
+
+struct bpf_fou_encap {
+	__be16 sport;
+	__be16 dport;
+};
+
+enum bpf_fou_encap_type {
+	FOU_BPF_ENCAP_FOU,
+	FOU_BPF_ENCAP_GUE,
+};
+
+__bpf_kfunc_start_defs();
+
+/* bpf_skb_set_fou_encap - Set FOU encap parameters
+ *
+ * This function allows for using GUE or FOU encapsulation together with an
+ * ipip device in collect-metadata mode.
+ *
+ * It is meant to be used in BPF tc-hooks and after a call to the
+ * bpf_skb_set_tunnel_key helper, responsible for setting IP addresses.
+ *
+ * Parameters:
+ * @skb_ctx	Pointer to ctx (__sk_buff) in TC program. Cannot be NULL
+ * @encap	Pointer to a `struct bpf_fou_encap` storing UDP src and
+ * 		dst ports. If sport is set to 0 the kernel will auto-assign a
+ * 		port. This is similar to using `encap-sport auto`.
+ * 		Cannot be NULL
+ * @type	Encapsulation type for the packet. Their definitions are
+ * 		specified in `enum bpf_fou_encap_type`
+ */
+__bpf_kfunc int bpf_skb_set_fou_encap(struct __sk_buff *skb_ctx,
+				      struct bpf_fou_encap *encap, int type)
+{
+	struct sk_buff *skb = (struct sk_buff *)skb_ctx;
+	struct ip_tunnel_info *info = skb_tunnel_info(skb);
+
+	if (unlikely(!encap))
+		return -EINVAL;
+
+	if (unlikely(!info || !(info->mode & IP_TUNNEL_INFO_TX)))
+		return -EINVAL;
+
+	switch (type) {
+	case FOU_BPF_ENCAP_FOU:
+		info->encap.type = TUNNEL_ENCAP_FOU;
+		break;
+	case FOU_BPF_ENCAP_GUE:
+		info->encap.type = TUNNEL_ENCAP_GUE;
+		break;
+	default:
+		info->encap.type = TUNNEL_ENCAP_NONE;
+	}
+
+	if (test_bit(IP_TUNNEL_CSUM_BIT, info->key.tun_flags))
+		info->encap.flags |= TUNNEL_ENCAP_FLAG_CSUM;
+
+	info->encap.sport = encap->sport;
+	info->encap.dport = encap->dport;
+
+	return 0;
+}
+
+/* bpf_skb_get_fou_encap - Get FOU encap parameters
+ *
+ * This function allows for reading encap metadata from a packet received
+ * on an ipip device in collect-metadata mode.
+ *
+ * Parameters:
+ * @skb_ctx	Pointer to ctx (__sk_buff) in TC program. Cannot be NULL
+ * @encap	Pointer to a struct bpf_fou_encap storing UDP source and
+ * 		destination port. Cannot be NULL
+ */
+__bpf_kfunc int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx,
+				      struct bpf_fou_encap *encap)
+{
+	struct sk_buff *skb = (struct sk_buff *)skb_ctx;
+	struct ip_tunnel_info *info = skb_tunnel_info(skb);
+
+	if (unlikely(!info))
+		return -EINVAL;
+
+	encap->sport = info->encap.sport;
+	encap->dport = info->encap.dport;
+
+	return 0;
+}
+
+__bpf_kfunc_end_defs();
+
+BTF_KFUNCS_START(fou_kfunc_set)
+BTF_ID_FLAGS(func, bpf_skb_set_fou_encap)
+BTF_ID_FLAGS(func, bpf_skb_get_fou_encap)
+BTF_KFUNCS_END(fou_kfunc_set)
+
+static const struct btf_kfunc_id_set fou_bpf_kfunc_set = {
+	.owner = THIS_MODULE,
+	.set   = &fou_kfunc_set,
+};
+
+int register_fou_bpf(void)
+{
+	return register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS,
+					 &fou_bpf_kfunc_set);
+}