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, 20 insertions, 0 deletions

diff --git a/tools/perf/util/mem2node.h b/tools/perf/util/mem2node.h
new file mode 100644
index 000000000..8dfa2b58d
--- /dev/null
+++ b/tools/perf/util/mem2node.h
@@ -0,0 +1,20 @@
+#ifndef __MEM2NODE_H
+#define __MEM2NODE_H
+
+#include <linux/rbtree.h>
+#include <linux/types.h>
+
+struct perf_env;
+struct phys_entry;
+
+struct mem2node {
+	struct rb_root		 root;
+	struct phys_entry	*entries;
+	int			 cnt;
+};
+
+int  mem2node__init(struct mem2node *map, struct perf_env *env);
+void mem2node__exit(struct mem2node *map);
+int  mem2node__node(struct mem2node *map, u64 addr);
+
+#endif /* __MEM2NODE_H */