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, 39 insertions, 0 deletions

diff --git a/drivers/interconnect/qcom/icc-common.c b/drivers/interconnect/qcom/icc-common.c
new file mode 100644
index 000000000..a25564fe1
--- /dev/null
+++ b/drivers/interconnect/qcom/icc-common.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Linaro Ltd.
+ */
+
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include "icc-common.h"
+
+struct icc_node_data *qcom_icc_xlate_extended(const struct of_phandle_args *spec,
+					      void *data)
+{
+	struct icc_node_data *ndata;
+	struct icc_node *node;
+
+	node = of_icc_xlate_onecell(spec, data);
+	if (IS_ERR(node))
+		return ERR_CAST(node);
+
+	ndata = kzalloc_obj(*ndata);
+	if (!ndata)
+		return ERR_PTR(-ENOMEM);
+
+	ndata->node = node;
+
+	if (spec->args_count == 2)
+		ndata->tag = spec->args[1];
+
+	if (spec->args_count > 2)
+		pr_warn("%pOF: Too many arguments, path tag is not parsed\n", spec->np);
+
+	return ndata;
+}
+EXPORT_SYMBOL_GPL(qcom_icc_xlate_extended);
+
+MODULE_DESCRIPTION("Qualcomm interconnect common functions");
+MODULE_LICENSE("GPL");