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, 28 insertions, 0 deletions

diff --git a/tools/perf/util/sample-raw.c b/tools/perf/util/sample-raw.c
new file mode 100644
index 000000000..e20b73c0c
--- /dev/null
+++ b/tools/perf/util/sample-raw.c
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include "sample-raw.h"
+
+#include <elf.h>
+#include <linux/string.h>
+
+#include "env.h"
+#include "evlist.h"
+#include "header.h"
+#include "session.h"
+
+/*
+ * Check platform the perf data file was created on and perform platform
+ * specific interpretation.
+ */
+void evlist__init_trace_event_sample_raw(struct evlist *evlist, struct perf_env *env)
+{
+	uint16_t e_machine = perf_env__e_machine(env, /*e_flags=*/NULL);
+
+	if (e_machine == EM_S390) {
+		evlist->trace_event_sample_raw = evlist__s390_sample_raw;
+	} else if (e_machine == EM_X86_64 || e_machine == EM_386) {
+		const char *cpuid = perf_env__cpuid(env);
+
+		if (cpuid && strstarts(cpuid, "AuthenticAMD") && evlist__has_amd_ibs(evlist))
+			evlist->trace_event_sample_raw = evlist__amd_sample_raw;
+	}
+}