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, 142 insertions, 0 deletions

diff --git a/tools/perf/util/target.c b/tools/perf/util/target.c
new file mode 100644
index 000000000..8cf71bea2
--- /dev/null
+++ b/tools/perf/util/target.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Helper functions for handling target threads/cpus
+ *
+ * Copyright (C) 2012, LG Electronics, Namhyung Kim <namhyung.kim@lge.com>
+ */
+
+#include "target.h"
+
+#include <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+
+enum target_errno target__validate(struct target *target)
+{
+	enum target_errno ret = TARGET_ERRNO__SUCCESS;
+
+	if (target->pid)
+		target->tid = target->pid;
+
+	/* CPU and PID are mutually exclusive */
+	if (target->tid && target->cpu_list) {
+		target->cpu_list = NULL;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__PID_OVERRIDE_CPU;
+	}
+
+	/* PID and SYSTEM are mutually exclusive */
+	if (target->tid && target->system_wide) {
+		target->system_wide = false;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__PID_OVERRIDE_SYSTEM;
+	}
+
+	/* BPF and CPU are mutually exclusive */
+	if (target->bpf_str && target->cpu_list) {
+		target->cpu_list = NULL;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_CPU;
+	}
+
+	/* BPF and PID/TID are mutually exclusive */
+	if (target->bpf_str && target->tid) {
+		target->tid = NULL;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_PID;
+	}
+
+	/* BPF and THREADS are mutually exclusive */
+	if (target->bpf_str && target->per_thread) {
+		target->per_thread = false;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_THREAD;
+	}
+
+	/* THREAD and SYSTEM/CPU are mutually exclusive */
+	if (target->per_thread && (target->system_wide || target->cpu_list)) {
+		target->per_thread = false;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__SYSTEM_OVERRIDE_THREAD;
+	}
+
+	return ret;
+}
+
+uid_t parse_uid(const char *str)
+{
+	struct passwd pwd, *result;
+	char buf[1024];
+
+	if (str == NULL)
+		return UINT_MAX;
+
+	/* Try user name first */
+	getpwnam_r(str, &pwd, buf, sizeof(buf), &result);
+
+	if (result == NULL) {
+		/*
+		 * The user name not found. Maybe it's a UID number.
+		 */
+		char *endptr;
+		int uid = strtol(str, &endptr, 10);
+
+		if (*endptr != '\0')
+			return UINT_MAX;
+
+		getpwuid_r(uid, &pwd, buf, sizeof(buf), &result);
+
+		if (result == NULL)
+			return UINT_MAX;
+	}
+
+	return result->pw_uid;
+}
+
+/*
+ * This must have a same ordering as the enum target_errno.
+ */
+static const char *target__error_str[] = {
+	"PID/TID switch overriding CPU",
+	"PID/TID switch overriding SYSTEM",
+	"SYSTEM/CPU switch overriding PER-THREAD",
+	"BPF switch overriding CPU",
+	"BPF switch overriding PID/TID",
+	"BPF switch overriding THREAD",
+};
+
+int target__strerror(struct target *target __maybe_unused, int errnum,
+			  char *buf, size_t buflen)
+{
+	int idx;
+	const char *msg;
+
+	BUG_ON(buflen == 0);
+
+	if (errnum >= 0) {
+		str_error_r(errnum, buf, buflen);
+		return 0;
+	}
+
+	if (errnum <  __TARGET_ERRNO__START || errnum >= __TARGET_ERRNO__END)
+		return -1;
+
+	idx = errnum - __TARGET_ERRNO__START;
+	msg = target__error_str[idx];
+
+	switch (errnum) {
+	case TARGET_ERRNO__PID_OVERRIDE_CPU ...
+	     TARGET_ERRNO__BPF_OVERRIDE_THREAD:
+		snprintf(buf, buflen, "%s", msg);
+		break;
+
+	default:
+		/* cannot reach here */
+		break;
+	}
+
+	return 0;
+}