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, 80 insertions, 0 deletions

diff --git a/drivers/soc/apple/tunable.c b/drivers/soc/apple/tunable.c
new file mode 100644
index 000000000..659323839
--- /dev/null
+++ b/drivers/soc/apple/tunable.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple Silicon hardware tunable support
+ *
+ * Each tunable is a list with each entry containing a offset into the MMIO
+ * region, a mask of bits to be cleared and a set of bits to be set. These
+ * tunables are passed along by the previous boot stages and vary from device
+ * to device such that they cannot be hardcoded in the individual drivers.
+ *
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/overflow.h>
+#include <linux/soc/apple/tunable.h>
+
+struct apple_tunable *devm_apple_tunable_parse(struct device *dev,
+					       struct device_node *np,
+					       const char *name,
+					       struct resource *res)
+{
+	struct apple_tunable *tunable;
+	struct property *prop;
+	const __be32 *p;
+	size_t sz;
+	int i;
+
+	if (resource_size(res) < 4)
+		return ERR_PTR(-EINVAL);
+
+	prop = of_find_property(np, name, NULL);
+	if (!prop)
+		return ERR_PTR(-ENOENT);
+
+	if (prop->length % (3 * sizeof(u32)))
+		return ERR_PTR(-EINVAL);
+	sz = prop->length / (3 * sizeof(u32));
+
+	tunable = devm_kzalloc(dev, struct_size(tunable, values, sz), GFP_KERNEL);
+	if (!tunable)
+		return ERR_PTR(-ENOMEM);
+	tunable->sz = sz;
+
+	for (i = 0, p = NULL; i < tunable->sz; ++i) {
+		p = of_prop_next_u32(prop, p, &tunable->values[i].offset);
+		p = of_prop_next_u32(prop, p, &tunable->values[i].mask);
+		p = of_prop_next_u32(prop, p, &tunable->values[i].value);
+
+		/* Sanity checks to catch bugs in our bootloader */
+		if (tunable->values[i].offset % 4)
+			return ERR_PTR(-EINVAL);
+		if (tunable->values[i].offset > (resource_size(res) - 4))
+			return ERR_PTR(-EINVAL);
+	}
+
+	return tunable;
+}
+EXPORT_SYMBOL(devm_apple_tunable_parse);
+
+void apple_tunable_apply(void __iomem *regs, struct apple_tunable *tunable)
+{
+	size_t i;
+
+	for (i = 0; i < tunable->sz; ++i) {
+		u32 val, old_val;
+
+		old_val = readl(regs + tunable->values[i].offset);
+		val = old_val & ~tunable->values[i].mask;
+		val |= tunable->values[i].value;
+		if (val != old_val)
+			writel(val, regs + tunable->values[i].offset);
+	}
+}
+EXPORT_SYMBOL(apple_tunable_apply);
+
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_AUTHOR("Sven Peter <sven@kernel.org>");
+MODULE_DESCRIPTION("Apple Silicon hardware tunable support");