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, 78 insertions, 0 deletions

diff --git a/fs/udf/udfend.h b/fs/udf/udfend.h
new file mode 100644
index 000000000..a4363ac2c
--- /dev/null
+++ b/fs/udf/udfend.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UDF_ENDIAN_H
+#define __UDF_ENDIAN_H
+
+#include <asm/byteorder.h>
+#include <linux/string.h>
+
+static inline struct kernel_lb_addr lelb_to_cpu(struct lb_addr in)
+{
+	struct kernel_lb_addr out;
+
+	out.logicalBlockNum = le32_to_cpu(in.logicalBlockNum);
+	out.partitionReferenceNum = le16_to_cpu(in.partitionReferenceNum);
+
+	return out;
+}
+
+static inline struct lb_addr cpu_to_lelb(struct kernel_lb_addr in)
+{
+	struct lb_addr out;
+
+	out.logicalBlockNum = cpu_to_le32(in.logicalBlockNum);
+	out.partitionReferenceNum = cpu_to_le16(in.partitionReferenceNum);
+
+	return out;
+}
+
+static inline struct short_ad lesa_to_cpu(struct short_ad in)
+{
+	struct short_ad out;
+
+	out.extLength = le32_to_cpu(in.extLength);
+	out.extPosition = le32_to_cpu(in.extPosition);
+
+	return out;
+}
+
+static inline struct short_ad cpu_to_lesa(struct short_ad in)
+{
+	struct short_ad out;
+
+	out.extLength = cpu_to_le32(in.extLength);
+	out.extPosition = cpu_to_le32(in.extPosition);
+
+	return out;
+}
+
+static inline struct kernel_long_ad lela_to_cpu(struct long_ad in)
+{
+	struct kernel_long_ad out;
+
+	out.extLength = le32_to_cpu(in.extLength);
+	out.extLocation = lelb_to_cpu(in.extLocation);
+
+	return out;
+}
+
+static inline struct long_ad cpu_to_lela(struct kernel_long_ad in)
+{
+	struct long_ad out;
+
+	out.extLength = cpu_to_le32(in.extLength);
+	out.extLocation = cpu_to_lelb(in.extLocation);
+
+	return out;
+}
+
+static inline struct kernel_extent_ad leea_to_cpu(struct extent_ad in)
+{
+	struct kernel_extent_ad out;
+
+	out.extLength = le32_to_cpu(in.extLength);
+	out.extLocation = le32_to_cpu(in.extLocation);
+
+	return out;
+}
+
+#endif /* __UDF_ENDIAN_H */