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, 73 insertions, 0 deletions

diff --git a/tools/perf/util/bpf-event.h b/tools/perf/util/bpf-event.h
new file mode 100644
index 000000000..da4eeb4a1
--- /dev/null
+++ b/tools/perf/util/bpf-event.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_BPF_EVENT_H
+#define __PERF_BPF_EVENT_H
+
+#include <linux/compiler.h>
+#include <linux/rbtree.h>
+#include <api/fd/array.h>
+#include <stdio.h>
+
+struct bpf_prog_info;
+struct machine;
+union perf_event;
+struct perf_env;
+struct perf_sample;
+struct perf_session;
+struct record_opts;
+struct evlist;
+struct target;
+
+struct bpf_metadata {
+	union perf_event *event;
+	char		 **prog_names;
+	__u64		 nr_prog_names;
+};
+
+struct bpf_prog_info_node {
+	struct perf_bpil		*info_linear;
+	struct bpf_metadata		*metadata;
+	struct rb_node			rb_node;
+};
+
+struct btf_node {
+	struct rb_node	rb_node;
+	u32		id;
+	u32		data_size;
+	char		data[];
+};
+
+#ifdef HAVE_LIBBPF_SUPPORT
+int machine__process_bpf(struct machine *machine, union perf_event *event,
+			 struct perf_sample *sample);
+int evlist__add_bpf_sb_event(struct evlist *evlist, struct perf_env *env);
+void __bpf_event__print_bpf_prog_info(struct perf_bpil *info_linear,
+				      struct perf_env *env,
+				      FILE *fp);
+void bpf_metadata_free(struct bpf_metadata *metadata);
+#else
+static inline int machine__process_bpf(struct machine *machine __maybe_unused,
+				       union perf_event *event __maybe_unused,
+				       struct perf_sample *sample __maybe_unused)
+{
+	return 0;
+}
+
+static inline int evlist__add_bpf_sb_event(struct evlist *evlist __maybe_unused,
+					   struct perf_env *env __maybe_unused)
+{
+	return 0;
+}
+
+static inline void __bpf_event__print_bpf_prog_info(struct perf_bpil *info_linear __maybe_unused,
+						    struct perf_env *env __maybe_unused,
+						    FILE *fp __maybe_unused)
+{
+
+}
+
+static inline void bpf_metadata_free(struct bpf_metadata *metadata __maybe_unused)
+{
+
+}
+#endif // HAVE_LIBBPF_SUPPORT
+#endif