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, 115 insertions, 0 deletions

diff --git a/tools/perf/util/parse-branch-options.c b/tools/perf/util/parse-branch-options.c
new file mode 100644
index 000000000..f7f7aff3d
--- /dev/null
+++ b/tools/perf/util/parse-branch-options.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "util/debug.h"
+#include "util/event.h"
+#include <subcmd/parse-options.h>
+#include "util/parse-branch-options.h"
+#include <stdlib.h>
+#include <string.h>
+
+#define BRANCH_OPT(n, m) \
+	{ .name = n, .mode = (m) }
+
+#define BRANCH_END { .name = NULL }
+
+struct branch_mode {
+	const char *name;
+	int mode;
+};
+
+static const struct branch_mode branch_modes[] = {
+	BRANCH_OPT("u", PERF_SAMPLE_BRANCH_USER),
+	BRANCH_OPT("k", PERF_SAMPLE_BRANCH_KERNEL),
+	BRANCH_OPT("hv", PERF_SAMPLE_BRANCH_HV),
+	BRANCH_OPT("any", PERF_SAMPLE_BRANCH_ANY),
+	BRANCH_OPT("any_call", PERF_SAMPLE_BRANCH_ANY_CALL),
+	BRANCH_OPT("any_ret", PERF_SAMPLE_BRANCH_ANY_RETURN),
+	BRANCH_OPT("ind_call", PERF_SAMPLE_BRANCH_IND_CALL),
+	BRANCH_OPT("abort_tx", PERF_SAMPLE_BRANCH_ABORT_TX),
+	BRANCH_OPT("in_tx", PERF_SAMPLE_BRANCH_IN_TX),
+	BRANCH_OPT("no_tx", PERF_SAMPLE_BRANCH_NO_TX),
+	BRANCH_OPT("cond", PERF_SAMPLE_BRANCH_COND),
+	BRANCH_OPT("ind_jmp", PERF_SAMPLE_BRANCH_IND_JUMP),
+	BRANCH_OPT("call", PERF_SAMPLE_BRANCH_CALL),
+	BRANCH_OPT("no_flags", PERF_SAMPLE_BRANCH_NO_FLAGS),
+	BRANCH_OPT("no_cycles", PERF_SAMPLE_BRANCH_NO_CYCLES),
+	BRANCH_OPT("save_type", PERF_SAMPLE_BRANCH_TYPE_SAVE),
+	BRANCH_OPT("stack", PERF_SAMPLE_BRANCH_CALL_STACK),
+	BRANCH_OPT("hw_index", PERF_SAMPLE_BRANCH_HW_INDEX),
+	BRANCH_OPT("priv", PERF_SAMPLE_BRANCH_PRIV_SAVE),
+	BRANCH_OPT("counter", PERF_SAMPLE_BRANCH_COUNTERS),
+	BRANCH_END
+};
+
+int parse_branch_str(const char *str, __u64 *mode)
+{
+#define ONLY_PLM \
+	(PERF_SAMPLE_BRANCH_USER	|\
+	 PERF_SAMPLE_BRANCH_KERNEL	|\
+	 PERF_SAMPLE_BRANCH_HV)
+
+	int ret = 0;
+	char *p, *s;
+	char *os = NULL;
+	const struct branch_mode *br;
+
+	if (str == NULL) {
+		*mode = PERF_SAMPLE_BRANCH_ANY;
+		return 0;
+	}
+
+	/* because str is read-only */
+	s = os = strdup(str);
+	if (!s)
+		return -1;
+
+	for (;;) {
+		p = strchr(s, ',');
+		if (p)
+			*p = '\0';
+
+		for (br = branch_modes; br->name; br++) {
+			if (!strcasecmp(s, br->name))
+				break;
+		}
+		if (!br->name) {
+			ret = -1;
+			pr_warning("unknown branch filter %s,"
+				    " check man page\n", s);
+			goto error;
+		}
+
+		*mode |= br->mode;
+
+		if (!p)
+			break;
+
+		s = p + 1;
+	}
+
+	/* default to any branch */
+	if ((*mode & ~ONLY_PLM) == 0) {
+		*mode = PERF_SAMPLE_BRANCH_ANY;
+	}
+error:
+	free(os);
+	return ret;
+}
+
+int
+parse_branch_stack(const struct option *opt, const char *str, int unset)
+{
+	__u64 *mode = (__u64 *)opt->value;
+
+	if (unset)
+		return 0;
+
+	/*
+	 * cannot set it twice, -b + --branch-filter for instance
+	 */
+	if (*mode) {
+		pr_err("Error: Can't use --branch-any (-b) with --branch-filter (-j).\n");
+		return -1;
+	}
+
+	return parse_branch_str(str, mode);
+}