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, 30 insertions, 0 deletions

diff --git a/include/soc/mediatek/smi.h b/include/soc/mediatek/smi.h
new file mode 100644
index 000000000..000eb1cf6
--- /dev/null
+++ b/include/soc/mediatek/smi.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2015-2016 MediaTek Inc.
+ * Author: Yong Wu <yong.wu@mediatek.com>
+ */
+#ifndef MTK_IOMMU_SMI_H
+#define MTK_IOMMU_SMI_H
+
+#include <linux/bitops.h>
+#include <linux/device.h>
+
+#if IS_ENABLED(CONFIG_MTK_SMI)
+
+enum iommu_atf_cmd {
+	IOMMU_ATF_CMD_CONFIG_SMI_LARB,		/* For mm master to en/disable iommu */
+	IOMMU_ATF_CMD_CONFIG_INFRA_IOMMU,	/* For infra master to enable iommu */
+	IOMMU_ATF_CMD_MAX,
+};
+
+#define MTK_SMI_MMU_EN(port)	BIT(port)
+
+struct mtk_smi_larb_iommu {
+	struct device *dev;
+	unsigned int   mmu;
+	unsigned char  bank[32];
+};
+
+#endif
+
+#endif