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, 139 insertions, 0 deletions

diff --git a/tools/perf/util/mem2node.c b/tools/perf/util/mem2node.c
new file mode 100644
index 000000000..51a2292cb
--- /dev/null
+++ b/tools/perf/util/mem2node.c
@@ -0,0 +1,139 @@
+#include <errno.h>
+#include <inttypes.h>
+#include <asm/bug.h>
+#include <linux/bitmap.h>
+#include <linux/kernel.h>
+#include <linux/zalloc.h>
+#include "debug.h"
+#include "env.h"
+#include "mem2node.h"
+
+struct phys_entry {
+	struct rb_node	rb_node;
+	u64	start;
+	u64	end;
+	u64	node;
+};
+
+static void phys_entry__insert(struct phys_entry *entry, struct rb_root *root)
+{
+	struct rb_node **p = &root->rb_node;
+	struct rb_node *parent = NULL;
+	struct phys_entry *e;
+
+	while (*p != NULL) {
+		parent = *p;
+		e = rb_entry(parent, struct phys_entry, rb_node);
+
+		if (entry->start < e->start)
+			p = &(*p)->rb_left;
+		else
+			p = &(*p)->rb_right;
+	}
+
+	rb_link_node(&entry->rb_node, parent, p);
+	rb_insert_color(&entry->rb_node, root);
+}
+
+static void
+phys_entry__init(struct phys_entry *entry, u64 start, u64 bsize, u64 node)
+{
+	entry->start = start;
+	entry->end   = start + bsize;
+	entry->node  = node;
+	RB_CLEAR_NODE(&entry->rb_node);
+}
+
+int mem2node__init(struct mem2node *map, struct perf_env *env)
+{
+	struct memory_node *n, *nodes = &env->memory_nodes[0];
+	struct phys_entry *entries, *tmp_entries;
+	u64 bsize = env->memory_bsize;
+	int i, j = 0, max = 0;
+
+	memset(map, 0x0, sizeof(*map));
+	map->root = RB_ROOT;
+
+	for (i = 0; i < env->nr_memory_nodes; i++) {
+		n = &nodes[i];
+		max += bitmap_weight(n->set, n->size);
+	}
+
+	entries = calloc(max, sizeof(*entries));
+	if (!entries)
+		return -ENOMEM;
+
+	for (i = 0; i < env->nr_memory_nodes; i++) {
+		u64 bit;
+
+		n = &nodes[i];
+
+		for (bit = 0; bit < n->size; bit++) {
+			u64 start;
+
+			if (!test_bit(bit, n->set))
+				continue;
+
+			start = bit * bsize;
+
+			/*
+			 * Merge nearby areas, we walk in order
+			 * through the bitmap, so no need to sort.
+			 */
+			if (j > 0) {
+				struct phys_entry *prev = &entries[j - 1];
+
+				if ((prev->end == start) &&
+				    (prev->node == n->node)) {
+					prev->end += bsize;
+					continue;
+				}
+			}
+
+			phys_entry__init(&entries[j++], start, bsize, n->node);
+		}
+	}
+
+	/* Cut unused entries, due to merging. */
+	tmp_entries = realloc(entries, sizeof(*entries) * j);
+	if (tmp_entries ||
+	    WARN_ONCE(j == 0, "No memory nodes, is CONFIG_MEMORY_HOTPLUG enabled?\n"))
+		entries = tmp_entries;
+
+	for (i = 0; i < j; i++) {
+		pr_debug("mem2node %03" PRIu64 " [0x%016" PRIx64 "-0x%016" PRIx64 "]\n",
+			 entries[i].node, entries[i].start, entries[i].end);
+
+		phys_entry__insert(&entries[i], &map->root);
+	}
+
+	map->entries = entries;
+	return 0;
+}
+
+void mem2node__exit(struct mem2node *map)
+{
+	zfree(&map->entries);
+}
+
+int mem2node__node(struct mem2node *map, u64 addr)
+{
+	struct rb_node **p, *parent = NULL;
+	struct phys_entry *entry;
+
+	p = &map->root.rb_node;
+	while (*p != NULL) {
+		parent = *p;
+		entry = rb_entry(parent, struct phys_entry, rb_node);
+		if (addr < entry->start)
+			p = &(*p)->rb_left;
+		else if (addr >= entry->end)
+			p = &(*p)->rb_right;
+		else
+			goto out;
+	}
+
+	entry = NULL;
+out:
+	return entry ? (int) entry->node : -1;
+}