[PATCH v4 xserver] test: Add a test for the overflow bug in bigreqs.

[Peter Hutterer]

From: Eric Anholt <eric at anholt.net>

The failing struct comes from the python test written by Michal Srb
<msrb at suse.com>.

v2: Use a drawable (root window) and gc, so that PolyLines hopefully
    actually tries processing things.  However, the request seems to
    process successfully so the poll() just stalls out.  However, this
    does let us distinguish between detecting the bigrequests error
    and not, at least.
v3: Clean up the description of what we expect the poll() call to do.
v4: change to use XISelectEvents

Signed-off-by: Eric Anholt <eric at anholt.net>
Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
Couldn't get v3 to crash here, even after changing to PolyRectangle. But I
found an easy to trigger test in XI2 - we know the server replies with
BadValue for a zero num_masks argument. So if we send a bigreq with a
num_masks 0 and a length 0, we can just check whether we get killed (good)
or a BadValue (bad). It doesn't test for specific memory overflows or
crashes, but based on the assumption that we shouldn't look at *any* BigReq
of size 0, this seems to be sufficient.

 test/bigreq/meson.build      |   8 ++++
 test/bigreq/request-length.c | 101 +++++++++++++++++++++++++++++++++++++++++++
 test/meson.build             |   1 +
 3 files changed, 110 insertions(+)
 create mode 100644 test/bigreq/meson.build
 create mode 100644 test/bigreq/request-length.c

diff --git a/test/bigreq/meson.build b/test/bigreq/meson.build
new file mode 100644
index 000000000..9462ede31
--- /dev/null
+++ b/test/bigreq/meson.build
@@ -0,0 +1,8 @@
+xcb_dep = dependency('xcb', required: false)
+
+if get_option('xvfb')
+    if xcb_dep.found()
+        requestlength = executable('request-length', 'request-length.c', dependencies: xcb_dep)
+        test('request-length', simple_xinit, args: [requestlength, '--', xvfb_server])
+    endif
+endif
diff --git a/test/bigreq/request-length.c b/test/bigreq/request-length.c
new file mode 100644
index 000000000..8174813ae
--- /dev/null
+++ b/test/bigreq/request-length.c
@@ -0,0 +1,101 @@
+/*
+ * Copyright © 2017 Broadcom
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <poll.h>
+#include <xcb/xcb.h>
+#include <xcb/bigreq.h>
+#include <xcb/xinput.h>
+
+int main(int argc, char **argv)
+{
+    xcb_connection_t *c = xcb_connect(NULL, NULL);
+    int fd = xcb_get_file_descriptor(c);
+
+    struct {
+        uint8_t extension;
+        uint8_t opcode;
+        uint16_t length;
+        uint32_t length_bigreq;
+        uint32_t win;
+        int num_masks;
+        uint16_t pad;
+    } xise_req = {
+        .extension = 0,
+        .opcode = XCB_INPUT_XI_SELECT_EVENTS,
+        /* The server triggers BadValue on a zero num_mask */
+        .num_masks = 0,
+        .win = 0,
+
+        /* This is the value that triggers the bug. */
+        .length_bigreq = 0,
+    };
+
+    xcb_query_extension_cookie_t cookie;
+    xcb_query_extension_reply_t *rep;
+
+    cookie = xcb_query_extension(c, 15, "XInputExtension");
+    rep = xcb_query_extension_reply(c, cookie, NULL);
+    xise_req.extension = rep->major_opcode;
+
+    free(xcb_big_requests_enable_reply(c, xcb_big_requests_enable(c), NULL));
+
+    /* Manually write out the bad request.  XCB can't help us here.*/
+    write(fd, &xise_req, sizeof(xise_req));
+
+    /* Block until the server has processed our mess and throws an
+     * error. If we get disconnected, then the server has noticed what we're
+     * up to. If we get an error back from the server, it looked at our fake
+     * request - which shouldn't happen.
+     */
+    struct pollfd pfd = {
+        .fd = fd,
+        .events = POLLIN,
+    };
+    poll(&pfd, 1, -1);
+
+    if (pfd.revents & POLLHUP) {
+        /* We got killed by the server for being naughty. Yay! */
+        return 0;
+    }
+
+    /* We didn't get disconnected, that's bad. If we get a BadValue from our
+     * request, we at least know that the bug triggered.
+     *
+     * If we get anything else back, something else has gone wrong.
+     */
+    xcb_generic_error_t error;
+    int r = read(fd, &error, sizeof(error));
+
+    if (r == sizeof(error) &&
+        error.error_code == 2 /* BadValue */  &&
+        error.major_code == xise_req.extension &&
+        error.minor_code == XCB_INPUT_XI_SELECT_EVENTS)
+        return 1; /* Our request was processed, which shouldn't happen */
+
+    /* Something else bad happened. We got something back but it's not the
+     * error we expected. If this happens, it needs to be investigated. */
+
+    return 2;
+}
diff --git a/test/meson.build b/test/meson.build
index 3e482d6f1..d413e9da5 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -23,4 +23,5 @@ if get_option('xvfb')
     endif
 endif
 
+subdir('bigreq')
 subdir('sync')
-- 
2.13.6