[LTP] [PATCH 3/4] syscalls/keyctl07: new test for oops when reading negative key

Eric Biggers
2017-10-10T17:51:19Z

Add a test for a bug which caused the kernel to dereference a bogus
pointer when using KEYCTL_READ to read from a negative key.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
runtest/syscalls | 1 +
testcases/kernel/syscalls/.gitignore | 1 +
testcases/kernel/syscalls/keyctl/keyctl07.c | 89 +++++++++++++++++++++++++++++
3 files changed, 91 insertions(+)
create mode 100644 testcases/kernel/syscalls/keyctl/keyctl07.c

diff --git a/runtest/syscalls b/runtest/syscalls
index 67a7362ee..649dbfa6c 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -501,6 +501,7 @@ keyctl03 keyctl03
keyctl04 keyctl04
keyctl05 keyctl05
keyctl06 keyctl06
+keyctl07 keyctl07

kcmp01 kcmp01
kcmp02 kcmp02
diff --git a/testcases/kernel/syscalls/.gitignore b/testcases/kernel/syscalls/.gitignore
index 1e573d9a4..53ad7ca2b 100644
--- a/testcases/kernel/syscalls/.gitignore
+++ b/testcases/kernel/syscalls/.gitignore
@@ -463,6 +463,7 @@
/keyctl/keyctl04
/keyctl/keyctl05
/keyctl/keyctl06
+/keyctl/keyctl07
/kcmp/kcmp01
/kcmp/kcmp02
/kcmp/kcmp03
diff --git a/testcases/kernel/syscalls/keyctl/keyctl07.c b/testcases/kernel/syscalls/keyctl/keyctl07.c
new file mode 100644
index 000000000..c41d7040f
--- /dev/null
+++ b/testcases/kernel/syscalls/keyctl/keyctl07.c
@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2017 Google, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program, if not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * Regression test for commit 37863c43b2c6 ("KEYS: prevent KEYCTL_READ on
+ * negative key").
+ */
+
+#include <errno.h>
+
+#include "tst_test.h"
+#include "lapi/keyctl.h"
+
+static void do_test(void)
+{
+ key_serial_t key_id;
+ char buffer[128];
+
+ /*
+ * Create a negatively instantiated key of the "user" key type. This
+ * key type is chosen because it has a ->read() method (which makes the
+ * bug reachable) and is available whenever CONFIG_KEYS is enabled.
+ *
+ * request_key() will result in the creation of a negative key provided
+ * that /sbin/request-key isn't configured to positively instantiate the
+ * key, based on the provided type, description, and callout_info. If
+ * /sbin/request-key doesn't exist, errno will be ENOENT; while if it
+ * does exist and we specify some random unprefixed description, errno
+ * should be ENOKEY (since /sbin/request-key should not be configured to
+ * instantiate random user keys). In either case a negative key should
+ * be created and we can continue on with the test. Negative keys last
+ * for 60 seconds so there should be plenty of time for the test.
+ */
+ TEST(request_key("user", "description", "callout_info",
+ KEY_SPEC_PROCESS_KEYRING));
+ if (TEST_RETURN != -1)
+ tst_brk(TBROK, "request_key() unexpectedly succeeded");
+
+ if (TEST_ERRNO != ENOKEY && TEST_ERRNO != ENOENT) {
+ tst_brk(TBROK | TTERRNO,
+ "request_key() failed with unexpected error");
+ }
+
+ /* Get the ID of the negative key by reading the keyring */
+ TEST(keyctl(KEYCTL_READ, KEY_SPEC_PROCESS_KEYRING,
+ &key_id, sizeof(key_id)));
+ if (TEST_RETURN < 0)
+ tst_brk(TBROK | TTERRNO, "KEYCTL_READ unexpectedly failed");
+ if (TEST_RETURN != sizeof(key_id)) {
+ tst_brk(TBROK, "KEYCTL_READ returned %ld but expected %zu",
+ TEST_RETURN, sizeof(key_id));
+ }
+
+ /*
+ * Now try to read the negative key. Unpatched kernels will oops trying
+ * to read from memory address 0x00000000ffffff92.
+ */
+ tst_res(TINFO, "trying to read from the negative key...");
+ TEST(keyctl(KEYCTL_READ, key_id, buffer, sizeof(buffer)));
+ if (TEST_RETURN != -1) {
+ tst_res(TFAIL,
+ "KEYCTL_READ on negative key unexpectedly succeeded");
+ return;
+ }
+ if (TEST_ERRNO != ENOKEY) {
+ tst_res(TFAIL | TTERRNO,
+ "KEYCTL_READ on negative key failed with unexpected error");
+ return;
+ }
+ tst_res(TPASS, "KEYCTL_READ on negative key expectedly failed with ENOKEY");
+}
+
+static struct tst_test test = {
+ .test_all = do_test,
+};
--
2.14.2.920.gcf0c67979c-goog