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, 99 insertions, 0 deletions

diff --git a/tools/perf/util/branch.h b/tools/perf/util/branch.h
new file mode 100644
index 000000000..a1d473649
--- /dev/null
+++ b/tools/perf/util/branch.h
@@ -0,0 +1,99 @@
+#ifndef _PERF_BRANCH_H
+#define _PERF_BRANCH_H 1
+/*
+ * The linux/stddef.h isn't need here, but is needed for __always_inline used
+ * in files included from uapi/linux/perf_event.h such as
+ * /usr/include/linux/swab.h and /usr/include/linux/byteorder/little_endian.h,
+ * detected in at least musl libc, used in Alpine Linux. -acme
+ */
+#include <stdio.h>
+#include <linux/perf_event.h>
+#include <linux/types.h>
+#include "util/map_symbol.h"
+#include "util/sample.h"
+
+struct branch_flags {
+	union {
+		u64 value;
+		struct {
+			u64 mispred:1;
+			u64 predicted:1;
+			u64 in_tx:1;
+			u64 abort:1;
+			u64 cycles:16;
+			u64 type:4;
+			u64 spec:2;
+			u64 new_type:4;
+			u64 priv:3;
+			u64 not_taken:1;
+			u64 reserved:30;
+		};
+	};
+};
+
+struct branch_info {
+	struct addr_map_symbol from;
+	struct addr_map_symbol to;
+	struct branch_flags    flags;
+	u64		       branch_stack_cntr;
+	char		       *srcline_from;
+	char		       *srcline_to;
+};
+
+struct branch_entry {
+	u64			from;
+	u64			to;
+	struct branch_flags	flags;
+};
+
+struct branch_stack {
+	u64			nr;
+	u64			hw_idx;
+	struct branch_entry	entries[];
+};
+
+/*
+ * The hw_idx is only available when PERF_SAMPLE_BRANCH_HW_INDEX is applied.
+ * Otherwise, the output format of a sample with branch stack is
+ * struct branch_stack {
+ *	u64			nr;
+ *	struct branch_entry	entries[0];
+ * }
+ * Check whether the hw_idx is available,
+ * and return the corresponding pointer of entries[0].
+ */
+static inline struct branch_entry *perf_sample__branch_entries(struct perf_sample *sample)
+{
+	u64 *entry = (u64 *)sample->branch_stack;
+
+	if (entry == NULL)
+		return NULL;
+
+	entry++;
+	if (sample->no_hw_idx)
+		return (struct branch_entry *)entry;
+	return (struct branch_entry *)(++entry);
+}
+
+struct branch_type_stat {
+	bool	branch_to;
+	u64	counts[PERF_BR_MAX];
+	u64	new_counts[PERF_BR_NEW_MAX];
+	u64	cond_fwd;
+	u64	cond_bwd;
+	u64	cross_4k;
+	u64	cross_2m;
+};
+
+void branch_type_count(struct branch_type_stat *st, struct branch_flags *flags,
+		       u64 from, u64 to);
+
+const char *branch_type_name(int type);
+const char *branch_new_type_name(int new_type);
+const char *get_branch_type(struct branch_entry *e);
+void branch_type_stat_display(FILE *fp, const struct branch_type_stat *st);
+int branch_type_str(const struct branch_type_stat *st, char *bf, int bfsize);
+
+const char *branch_spec_desc(int spec);
+
+#endif /* _PERF_BRANCH_H */