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, 52 insertions, 0 deletions

diff --git a/include/net/ife.h b/include/net/ife.h
new file mode 100644
index 000000000..7e2538d85
--- /dev/null
+++ b/include/net/ife.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NET_IFE_H
+#define __NET_IFE_H
+
+#include <linux/etherdevice.h>
+#include <linux/rtnetlink.h>
+#include <uapi/linux/ife.h>
+
+#if IS_ENABLED(CONFIG_NET_IFE)
+
+void *ife_encode(struct sk_buff *skb, u16 metalen);
+void *ife_decode(struct sk_buff *skb, u16 *metalen);
+
+void *ife_tlv_meta_decode(void *skbdata, const void *ifehdr_end, u16 *attrtype,
+			  u16 *dlen, u16 *totlen);
+int ife_tlv_meta_encode(void *skbdata, u16 attrtype, u16 dlen,
+			const void *dval);
+
+void *ife_tlv_meta_next(void *skbdata);
+
+#else
+
+static inline void *ife_encode(struct sk_buff *skb, u16 metalen)
+{
+	return NULL;
+}
+
+static inline void *ife_decode(struct sk_buff *skb, u16 *metalen)
+{
+	return NULL;
+}
+
+static inline void *ife_tlv_meta_decode(void *skbdata, u16 *attrtype, u16 *dlen,
+					u16 *totlen)
+{
+	return NULL;
+}
+
+static inline int ife_tlv_meta_encode(void *skbdata, u16 attrtype, u16 dlen,
+			const void *dval)
+{
+	return 0;
+}
+
+static inline void *ife_tlv_meta_next(void *skbdata)
+{
+	return NULL;
+}
+
+#endif
+
+#endif /* __NET_IFE_H */