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, 28 insertions, 0 deletions

diff --git a/io_uring/bpf-ops.h b/io_uring/bpf-ops.h
new file mode 100644
index 000000000..0b6d78949
--- /dev/null
+++ b/io_uring/bpf-ops.h
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef IOU_BPF_OPS_H
+#define IOU_BPF_OPS_H
+
+#include <linux/io_uring_types.h>
+
+enum {
+	IOU_REGION_MEM,
+	IOU_REGION_CQ,
+	IOU_REGION_SQ,
+};
+
+struct io_uring_bpf_ops {
+	int (*loop_step)(struct iou_ctx *, struct iou_loop_params *lp);
+
+	__u32 ring_fd;
+	void *priv;
+};
+
+#ifdef CONFIG_IO_URING_BPF_OPS
+void io_unregister_bpf_ops(struct io_ring_ctx *ctx);
+#else
+static inline void io_unregister_bpf_ops(struct io_ring_ctx *ctx)
+{
+}
+#endif
+
+#endif /* IOU_BPF_OPS_H */