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io: fix stack allocation when sending of file descriptors

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When sending file descriptors over a socket, we have to
allocate a data buffer to hold the FDs in the scmsghdr.
Unfortunately we allocated the buffer on the stack inside
an if () {} block, but called sendmsg() outside the block.
So the stack bytes holding the FDs were liable to be
overwritten with other data. By luck this was not a problem
when sending 1 FD, but if sending 2 or more then it would
fail.

The fix is to simply move the variables outside the nested
'if' block. To keep valgrind quiet we also zero-initialize
the 'control' buffer.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2015-12-21 11:58:51 +00:00
parent bead59946a
commit 7b3c618ad0
2 changed files with 99 additions and 4 deletions
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7
io/channel-socket.c
View file

@ -493,15 +493,14 @@ static ssize_t qio_channel_socket_writev(QIOChannel *ioc,
QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc);
ssize_t ret;
struct msghdr msg = { NULL, };
char control[CMSG_SPACE(sizeof(int) * SOCKET_MAX_FDS)] = { 0 };
size_t fdsize = sizeof(int) * nfds;
struct cmsghdr *cmsg;
msg.msg_iov = (struct iovec *)iov;
msg.msg_iovlen = niov;
if (nfds) {
char control[CMSG_SPACE(sizeof(int) * SOCKET_MAX_FDS)];
size_t fdsize = sizeof(int) * nfds;
struct cmsghdr *cmsg;
if (nfds > SOCKET_MAX_FDS) {
error_setg_errno(errp, -EINVAL,
"Only %d FDs can be sent, got %zu",

96
tests/test-io-channel-socket.c
View file

@ -376,6 +376,100 @@ static void test_io_channel_unix_async(void)
{
return test_io_channel_unix(true);
}
static void test_io_channel_unix_fd_pass(void)
{
SocketAddress *listen_addr = g_new0(SocketAddress, 1);
SocketAddress *connect_addr = g_new0(SocketAddress, 1);
QIOChannel *src, *dst;
int testfd;
int fdsend[3];
int *fdrecv = NULL;
size_t nfdrecv = 0;
size_t i;
char bufsend[12], bufrecv[12];
struct iovec iosend[1], iorecv[1];
#define TEST_SOCKET "test-io-channel-socket.sock"
#define TEST_FILE "test-io-channel-socket.txt"
testfd = open(TEST_FILE, O_RDWR|O_TRUNC|O_CREAT, 0700);
g_assert(testfd != -1);
fdsend[0] = testfd;
fdsend[1] = testfd;
fdsend[2] = testfd;
listen_addr->type = SOCKET_ADDRESS_KIND_UNIX;
listen_addr->u.q_unix = g_new0(UnixSocketAddress, 1);
listen_addr->u.q_unix->path = g_strdup(TEST_SOCKET);
connect_addr->type = SOCKET_ADDRESS_KIND_UNIX;
connect_addr->u.q_unix = g_new0(UnixSocketAddress, 1);
connect_addr->u.q_unix->path = g_strdup(TEST_SOCKET);
test_io_channel_setup_sync(listen_addr, connect_addr, &src, &dst);
memcpy(bufsend, "Hello World", G_N_ELEMENTS(bufsend));
iosend[0].iov_base = bufsend;
iosend[0].iov_len = G_N_ELEMENTS(bufsend);
iorecv[0].iov_base = bufrecv;
iorecv[0].iov_len = G_N_ELEMENTS(bufrecv);
g_assert(qio_channel_has_feature(src, QIO_CHANNEL_FEATURE_FD_PASS));
g_assert(qio_channel_has_feature(dst, QIO_CHANNEL_FEATURE_FD_PASS));
qio_channel_writev_full(src,
iosend,
G_N_ELEMENTS(iosend),
fdsend,
G_N_ELEMENTS(fdsend),
&error_abort);
qio_channel_readv_full(dst,
iorecv,
G_N_ELEMENTS(iorecv),
&fdrecv,
&nfdrecv,
&error_abort);
g_assert(nfdrecv == G_N_ELEMENTS(fdsend));
/* Each recvd FD should be different from sent FD */
for (i = 0; i < nfdrecv; i++) {
g_assert_cmpint(fdrecv[i], !=, testfd);
}
/* Each recvd FD should be different from each other */
g_assert_cmpint(fdrecv[0], !=, fdrecv[1]);
g_assert_cmpint(fdrecv[0], !=, fdrecv[2]);
g_assert_cmpint(fdrecv[1], !=, fdrecv[2]);
/* Check the I/O buf we sent at the same time matches */
g_assert(memcmp(bufsend, bufrecv, G_N_ELEMENTS(bufsend)) == 0);
/* Write some data into the FD we received */
g_assert(write(fdrecv[0], bufsend, G_N_ELEMENTS(bufsend)) ==
G_N_ELEMENTS(bufsend));
/* Read data from the original FD and make sure it matches */
memset(bufrecv, 0, G_N_ELEMENTS(bufrecv));
g_assert(lseek(testfd, 0, SEEK_SET) == 0);
g_assert(read(testfd, bufrecv, G_N_ELEMENTS(bufrecv)) ==
G_N_ELEMENTS(bufrecv));
g_assert(memcmp(bufsend, bufrecv, G_N_ELEMENTS(bufsend)) == 0);
object_unref(OBJECT(src));
object_unref(OBJECT(dst));
qapi_free_SocketAddress(listen_addr);
qapi_free_SocketAddress(connect_addr);
unlink(TEST_SOCKET);
unlink(TEST_FILE);
close(testfd);
for (i = 0; i < nfdrecv; i++) {
close(fdrecv[i]);
}
g_free(fdrecv);
}
#endif /* _WIN32 */
@ -414,6 +508,8 @@ int main(int argc, char **argv)
test_io_channel_unix_sync);
g_test_add_func("/io/channel/socket/unix-async",
test_io_channel_unix_async);
g_test_add_func("/io/channel/socket/unix-fd-pass",
test_io_channel_unix_fd_pass);
#endif /* _WIN32 */
return g_test_run();