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, 58 insertions, 0 deletions

diff --git a/io_uring/opdef.h b/io_uring/opdef.h
new file mode 100644
index 000000000..667f981e6
--- /dev/null
+++ b/io_uring/opdef.h
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef IOU_OP_DEF_H
+#define IOU_OP_DEF_H
+
+struct io_uring_bpf_ctx;
+
+struct io_issue_def {
+	/* needs req->file assigned */
+	unsigned		needs_file : 1;
+	/* should block plug */
+	unsigned		plug : 1;
+	/* supports ioprio */
+	unsigned		ioprio : 1;
+	/* supports iopoll */
+	unsigned		iopoll : 1;
+	/* op supports buffer selection */
+	unsigned		buffer_select : 1;
+	/* hash wq insertion if file is a regular file */
+	unsigned		hash_reg_file : 1;
+	/* unbound wq insertion if file is a non-regular file */
+	unsigned		unbound_nonreg_file : 1;
+	/* set if opcode supports polled "wait" */
+	unsigned		pollin : 1;
+	unsigned		pollout : 1;
+	unsigned		poll_exclusive : 1;
+	/* skip auditing */
+	unsigned		audit_skip : 1;
+	/* vectored opcode, set if 1) vectored, and 2) handler needs to know */
+	unsigned		vectored : 1;
+	/* set to 1 if this opcode uses 128b sqes in a mixed sq */
+	unsigned		is_128 : 1;
+
+	/* size of async data needed, if any */
+	unsigned short		async_size;
+
+	/* bpf filter pdu size, if any */
+	unsigned short		filter_pdu_size;
+
+	int (*issue)(struct io_kiocb *, unsigned int);
+	int (*prep)(struct io_kiocb *, const struct io_uring_sqe *);
+	void (*filter_populate)(struct io_uring_bpf_ctx *, struct io_kiocb *);
+};
+
+struct io_cold_def {
+	const char		*name;
+
+	void (*sqe_copy)(struct io_kiocb *);
+	void (*cleanup)(struct io_kiocb *);
+	void (*fail)(struct io_kiocb *);
+};
+
+extern const struct io_issue_def io_issue_defs[];
+extern const struct io_cold_def io_cold_defs[];
+
+bool io_uring_op_supported(u8 opcode);
+
+void io_uring_optable_init(void);
+#endif