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, 70 insertions, 0 deletions

diff --git a/tools/perf/util/parse-sublevel-options.c b/tools/perf/util/parse-sublevel-options.c
new file mode 100644
index 000000000..a841d17ff
--- /dev/null
+++ b/tools/perf/util/parse-sublevel-options.c
@@ -0,0 +1,70 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "util/debug.h"
+#include "util/parse-sublevel-options.h"
+
+static int parse_one_sublevel_option(const char *str,
+				     struct sublevel_option *opts)
+{
+	struct sublevel_option *opt = opts;
+	char *vstr, *s = strdup(str);
+	int v = 1;
+
+	if (!s) {
+		pr_err("no memory\n");
+		return -1;
+	}
+
+	vstr = strchr(s, '=');
+	if (vstr)
+		*vstr++ = 0;
+
+	while (opt->name) {
+		if (!strcmp(s, opt->name))
+			break;
+		opt++;
+	}
+
+	if (!opt->name) {
+		pr_err("Unknown option name '%s'\n", s);
+		free(s);
+		return -1;
+	}
+
+	if (vstr)
+		v = atoi(vstr);
+
+	*opt->value_ptr = v;
+	free(s);
+	return 0;
+}
+
+/* parse options like --foo a=<n>,b,c... */
+int perf_parse_sublevel_options(const char *str, struct sublevel_option *opts)
+{
+	char *s = strdup(str);
+	char *p = NULL;
+	int ret;
+
+	if (!s) {
+		pr_err("no memory\n");
+		return -1;
+	}
+
+	p = strtok(s, ",");
+	while (p) {
+		ret = parse_one_sublevel_option(p, opts);
+		if (ret) {
+			free(s);
+			return ret;
+		}
+
+		p = strtok(NULL, ",");
+	}
+
+	free(s);
+	return 0;
+}