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, 90 insertions, 0 deletions

diff --git a/tools/perf/util/perf-hooks.c b/tools/perf/util/perf-hooks.c
new file mode 100644
index 000000000..7a0ab3507
--- /dev/null
+++ b/tools/perf/util/perf-hooks.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * perf_hooks.c
+ *
+ * Copyright (C) 2016 Wang Nan <wangnan0@huawei.com>
+ * Copyright (C) 2016 Huawei Inc.
+ */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <setjmp.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include "util/debug.h"
+#include "util/perf-hooks.h"
+
+static sigjmp_buf jmpbuf;
+static const struct perf_hook_desc *current_perf_hook;
+
+void perf_hooks__invoke(const struct perf_hook_desc *desc)
+{
+	if (!(desc && desc->p_hook_func && *desc->p_hook_func))
+		return;
+
+	if (sigsetjmp(jmpbuf, 1)) {
+		pr_warning("Fatal error (SEGFAULT) in perf hook '%s'\n",
+			   desc->hook_name);
+		*(current_perf_hook->p_hook_func) = NULL;
+	} else {
+		current_perf_hook = desc;
+		(**desc->p_hook_func)(desc->hook_ctx);
+	}
+	current_perf_hook = NULL;
+}
+
+void perf_hooks__recover(void)
+{
+	if (current_perf_hook)
+		siglongjmp(jmpbuf, 1);
+}
+
+#define PERF_HOOK(name)					\
+perf_hook_func_t __perf_hook_func_##name = NULL;	\
+struct perf_hook_desc __perf_hook_desc_##name =		\
+	{.hook_name = #name,				\
+	 .p_hook_func = &__perf_hook_func_##name,	\
+	 .hook_ctx = NULL};
+#include "perf-hooks-list.h"
+#undef PERF_HOOK
+
+#define PERF_HOOK(name)		\
+	&__perf_hook_desc_##name,
+
+static struct perf_hook_desc *perf_hooks[] = {
+#include "perf-hooks-list.h"
+};
+#undef PERF_HOOK
+
+int perf_hooks__set_hook(const char *hook_name,
+			 perf_hook_func_t hook_func,
+			 void *hook_ctx)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(perf_hooks); i++) {
+		if (strcmp(hook_name, perf_hooks[i]->hook_name) != 0)
+			continue;
+
+		if (*(perf_hooks[i]->p_hook_func))
+			pr_warning("Overwrite existing hook: %s\n", hook_name);
+		*(perf_hooks[i]->p_hook_func) = hook_func;
+		perf_hooks[i]->hook_ctx = hook_ctx;
+		return 0;
+	}
+	return -ENOENT;
+}
+
+perf_hook_func_t perf_hooks__get_hook(const char *hook_name)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(perf_hooks); i++) {
+		if (strcmp(hook_name, perf_hooks[i]->hook_name) != 0)
+			continue;
+
+		return *(perf_hooks[i]->p_hook_func);
+	}
+	return ERR_PTR(-ENOENT);
+}