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, 142 insertions, 0 deletions

diff --git a/drivers/nvmem/rcar-efuse.c b/drivers/nvmem/rcar-efuse.c
new file mode 100644
index 000000000..b94ff83b7
--- /dev/null
+++ b/drivers/nvmem/rcar-efuse.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Renesas R-Car E-FUSE/OTP Driver
+ *
+ * Copyright (C) 2024 Glider bv
+ */
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/io.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/property.h>
+
+struct rcar_fuse {
+	struct nvmem_keepout keepouts[2];
+	struct nvmem_device *nvmem;
+	struct device *dev;
+	void __iomem *base;
+};
+
+struct rcar_fuse_data {
+	unsigned int bank;	/* 0: PFC + E-FUSE, 1: OPT_MEM + E-FUSE */
+	unsigned int start;	/* inclusive */
+	unsigned int end;	/* exclusive */
+};
+
+static int rcar_fuse_reg_read(void *priv, unsigned int offset, void *val,
+			      size_t bytes)
+{
+	struct rcar_fuse *fuse = priv;
+	int ret;
+
+	ret = pm_runtime_resume_and_get(fuse->dev);
+	if (ret < 0)
+		return ret;
+
+	__ioread32_copy(val, fuse->base + offset, bytes / 4);
+
+	pm_runtime_put(fuse->dev);
+
+	return 0;
+}
+
+static int rcar_fuse_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct rcar_fuse_data *data = device_get_match_data(dev);
+	struct nvmem_config config = {
+		.dev = dev,
+		.name = "rcar-fuse",
+		.id = NVMEM_DEVID_NONE,
+		.owner = THIS_MODULE,
+		.type = NVMEM_TYPE_OTP,
+		.read_only = true,
+		.root_only = true,
+		.reg_read = rcar_fuse_reg_read,
+		.word_size = 4,
+		.stride = 4,
+	};
+	struct rcar_fuse *fuse;
+	struct resource *res;
+	int ret;
+
+	ret = devm_pm_runtime_enable(dev);
+	if (ret < 0)
+		return ret;
+
+	fuse = devm_kzalloc(dev, sizeof(*fuse), GFP_KERNEL);
+	if (!fuse)
+		return -ENOMEM;
+
+	fuse->base = devm_platform_get_and_ioremap_resource(pdev, data->bank,
+							    &res);
+	if (IS_ERR(fuse->base))
+		return PTR_ERR(fuse->base);
+
+	fuse->dev = dev;
+	fuse->keepouts[0].start = 0;
+	fuse->keepouts[0].end = data->start;
+	fuse->keepouts[1].start = data->end;
+	fuse->keepouts[1].end = resource_size(res);
+
+	config.keepout = fuse->keepouts;
+	config.nkeepout = ARRAY_SIZE(fuse->keepouts);
+	config.size = resource_size(res);
+	config.priv = fuse;
+
+	fuse->nvmem = devm_nvmem_register(dev, &config);
+	if (IS_ERR(fuse->nvmem))
+		return dev_err_probe(dev, PTR_ERR(fuse->nvmem),
+				     "Failed to register NVMEM device\n");
+
+	return 0;
+}
+
+static const struct rcar_fuse_data rcar_fuse_v3u = {
+	.bank = 0,
+	.start = 0x0c0,
+	.end = 0x0e8,
+};
+
+static const struct rcar_fuse_data rcar_fuse_s4 = {
+	.bank = 0,
+	.start = 0x0c0,
+	.end = 0x14c,
+};
+
+static const struct rcar_fuse_data rcar_fuse_v4h = {
+	.bank = 1,
+	.start = 0x100,
+	.end = 0x1a0,
+};
+
+static const struct rcar_fuse_data rcar_fuse_v4m = {
+	.bank = 1,
+	.start = 0x100,
+	.end = 0x110,
+};
+
+static const struct of_device_id rcar_fuse_match[] = {
+	{ .compatible = "renesas,r8a779a0-efuse", .data = &rcar_fuse_v3u },
+	{ .compatible = "renesas,r8a779f0-efuse", .data = &rcar_fuse_s4 },
+	{ .compatible = "renesas,r8a779g0-otp", .data = &rcar_fuse_v4h },
+	{ .compatible = "renesas,r8a779h0-otp", .data = &rcar_fuse_v4m },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rcar_fuse_match);
+
+static struct platform_driver rcar_fuse_driver = {
+	.probe = rcar_fuse_probe,
+	.driver = {
+		.name = "rcar_fuse",
+		.of_match_table = rcar_fuse_match,
+	},
+};
+module_platform_driver(rcar_fuse_driver);
+
+MODULE_DESCRIPTION("Renesas R-Car E-FUSE/OTP driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Geert Uytterhoeven");