diff options
| -rw-r--r-- | pkg/sentry/socket/netlink/BUILD | 1 | ||||
| -rw-r--r-- | pkg/sentry/socket/netlink/socket.go | 22 | ||||
| -rw-r--r-- | test/syscalls/linux/socket_netlink_route.cc | 153 | ||||
| -rw-r--r-- | test/syscalls/linux/socket_netlink_util.cc | 7 |
4 files changed, 183 insertions, 0 deletions
diff --git a/pkg/sentry/socket/netlink/BUILD b/pkg/sentry/socket/netlink/BUILD index 45ebb2a0e..7da68384e 100644 --- a/pkg/sentry/socket/netlink/BUILD +++ b/pkg/sentry/socket/netlink/BUILD @@ -21,6 +21,7 @@ go_library( "//pkg/sentry/fs/fsutil", "//pkg/sentry/kernel", "//pkg/sentry/kernel/time", + "//pkg/sentry/safemem", "//pkg/sentry/socket", "//pkg/sentry/socket/netlink/port", "//pkg/sentry/socket/unix", diff --git a/pkg/sentry/socket/netlink/socket.go b/pkg/sentry/socket/netlink/socket.go index d0aab293d..b2732ca29 100644 --- a/pkg/sentry/socket/netlink/socket.go +++ b/pkg/sentry/socket/netlink/socket.go @@ -28,6 +28,7 @@ import ( "gvisor.dev/gvisor/pkg/sentry/fs/fsutil" "gvisor.dev/gvisor/pkg/sentry/kernel" ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time" + "gvisor.dev/gvisor/pkg/sentry/safemem" "gvisor.dev/gvisor/pkg/sentry/socket" "gvisor.dev/gvisor/pkg/sentry/socket/netlink/port" "gvisor.dev/gvisor/pkg/sentry/socket/unix" @@ -416,6 +417,24 @@ func (s *Socket) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags int, have Peek: flags&linux.MSG_PEEK != 0, } + // If MSG_TRUNC is set with a zero byte destination then we still need + // to read the message and discard it, or in the case where MSG_PEEK is + // set, leave it be. In both cases the full message length must be + // returned. However, the memory manager for the destination will not read + // the endpoint if the destination is zero length. + // + // In order for the endpoint to be read when the destination size is zero, + // we must cause a read of the endpoint by using a separate fake zero + // length block sequence and calling the EndpointReader directly. + if trunc && dst.Addrs.NumBytes() == 0 { + // Perform a read to a zero byte block sequence. We can ignore the + // original destination since it was zero bytes. The length returned by + // ReadToBlocks is ignored and we return the full message length to comply + // with MSG_TRUNC. + _, err := r.ReadToBlocks(safemem.BlockSeqOf(safemem.BlockFromSafeSlice(make([]byte, 0)))) + return int(r.MsgSize), linux.MSG_TRUNC, from, fromLen, socket.ControlMessages{}, syserr.FromError(err) + } + if n, err := dst.CopyOutFrom(t, &r); err != syserror.ErrWouldBlock || flags&linux.MSG_DONTWAIT != 0 { var mflags int if n < int64(r.MsgSize) { @@ -499,6 +518,9 @@ func (s *Socket) sendResponse(ctx context.Context, ms *MessageSet) *syserr.Error PortID: uint32(ms.PortID), }) + // Add the dump_done_errno payload. + m.Put(int64(0)) + _, notify, err := s.connection.Send([][]byte{m.Finalize()}, transport.ControlMessages{}, tcpip.FullAddress{}) if err != nil && err != syserr.ErrWouldBlock { return err diff --git a/test/syscalls/linux/socket_netlink_route.cc b/test/syscalls/linux/socket_netlink_route.cc index 32fe0d6d1..dd4a11655 100644 --- a/test/syscalls/linux/socket_netlink_route.cc +++ b/test/syscalls/linux/socket_netlink_route.cc @@ -539,6 +539,159 @@ TEST(NetlinkRouteTest, GetRouteDump) { EXPECT_TRUE(dstFound); } +// RecvmsgTrunc tests the recvmsg MSG_TRUNC flag with zero length output +// buffer. MSG_TRUNC with a zero length buffer should consume subsequent +// messages off the socket. +TEST(NetlinkRouteTest, RecvmsgTrunc) { + FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(NetlinkBoundSocket()); + + struct request { + struct nlmsghdr hdr; + struct rtgenmsg rgm; + }; + + constexpr uint32_t kSeq = 12345; + + struct request req; + req.hdr.nlmsg_len = sizeof(req); + req.hdr.nlmsg_type = RTM_GETADDR; + req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP; + req.hdr.nlmsg_seq = kSeq; + req.rgm.rtgen_family = AF_UNSPEC; + + struct iovec iov = {}; + iov.iov_base = &req; + iov.iov_len = sizeof(req); + + struct msghdr msg = {}; + msg.msg_iov = &iov; + msg.msg_iovlen = 1; + + ASSERT_THAT(RetryEINTR(sendmsg)(fd.get(), &msg, 0), SyscallSucceeds()); + + iov.iov_base = NULL; + iov.iov_len = 0; + + int trunclen, trunclen2; + + // Note: This test assumes at least two messages are returned by the + // RTM_GETADDR request. That means at least one RTM_NEWLINK message and one + // NLMSG_DONE message. We cannot read all the messages without blocking + // because we would need to read the message into a buffer and check the + // nlmsg_type for NLMSG_DONE. However, the test depends on reading into a + // zero-length buffer. + + // First, call recvmsg with MSG_TRUNC. This will read the full message from + // the socket and return it's full length. Subsequent calls to recvmsg will + // read the next messages from the socket. + ASSERT_THAT(trunclen = RetryEINTR(recvmsg)(fd.get(), &msg, MSG_TRUNC), + SyscallSucceeds()); + + // Message should always be truncated. However, While the destination iov is + // zero length, MSG_TRUNC returns the size of the next message so it should + // not be zero. + ASSERT_EQ(msg.msg_flags & MSG_TRUNC, MSG_TRUNC); + ASSERT_NE(trunclen, 0); + // Returned length is at least the header and ifaddrmsg. + EXPECT_GE(trunclen, sizeof(struct nlmsghdr) + sizeof(struct ifaddrmsg)); + + // Reset the msg_flags to make sure that the recvmsg call is setting them + // properly. + msg.msg_flags = 0; + + // Make a second recvvmsg call to get the next message. + ASSERT_THAT(trunclen2 = RetryEINTR(recvmsg)(fd.get(), &msg, MSG_TRUNC), + SyscallSucceeds()); + ASSERT_EQ(msg.msg_flags & MSG_TRUNC, MSG_TRUNC); + ASSERT_NE(trunclen2, 0); + + // Assert that the received messages are not the same. + // + // We are calling recvmsg with a zero length buffer so we have no way to + // inspect the messages to make sure they are not equal in value. The best + // we can do is to compare their lengths. + ASSERT_NE(trunclen, trunclen2); +} + +// RecvmsgTruncPeek tests recvmsg with the combination of the MSG_TRUNC and +// MSG_PEEK flags and a zero length output buffer. This is normally used to +// read the full length of the next message on the socket without consuming +// it, so a properly sized buffer can be allocated to store the message. This +// test tests that scenario. +TEST(NetlinkRouteTest, RecvmsgTruncPeek) { + FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(NetlinkBoundSocket()); + + struct request { + struct nlmsghdr hdr; + struct rtgenmsg rgm; + }; + + constexpr uint32_t kSeq = 12345; + + struct request req; + req.hdr.nlmsg_len = sizeof(req); + req.hdr.nlmsg_type = RTM_GETADDR; + req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP; + req.hdr.nlmsg_seq = kSeq; + req.rgm.rtgen_family = AF_UNSPEC; + + struct iovec iov = {}; + iov.iov_base = &req; + iov.iov_len = sizeof(req); + + struct msghdr msg = {}; + msg.msg_iov = &iov; + msg.msg_iovlen = 1; + + ASSERT_THAT(RetryEINTR(sendmsg)(fd.get(), &msg, 0), SyscallSucceeds()); + + int type = -1; + do { + int peeklen; + int len; + + iov.iov_base = NULL; + iov.iov_len = 0; + + // Call recvmsg with MSG_PEEK and MSG_TRUNC. This will peek at the message + // and return it's full length. + // See: MSG_TRUNC http://man7.org/linux/man-pages/man2/recv.2.html + ASSERT_THAT( + peeklen = RetryEINTR(recvmsg)(fd.get(), &msg, MSG_PEEK | MSG_TRUNC), + SyscallSucceeds()); + + // Message should always be truncated. + ASSERT_EQ(msg.msg_flags & MSG_TRUNC, MSG_TRUNC); + ASSERT_NE(peeklen, 0); + + // Reset the message flags for the next call. + msg.msg_flags = 0; + + // Make the actual call to recvmsg to get the actual data. We will use + // the length returned from the peek call for the allocated buffer size.. + std::vector<char> buf(peeklen); + iov.iov_base = buf.data(); + iov.iov_len = buf.size(); + ASSERT_THAT(len = RetryEINTR(recvmsg)(fd.get(), &msg, 0), + SyscallSucceeds()); + + // Message should not be truncated since we allocated the correct buffer + // size. + EXPECT_NE(msg.msg_flags & MSG_TRUNC, MSG_TRUNC); + + // MSG_PEEK should have left data on the socket and the subsequent call + // with should have retrieved the same data. Both calls should have + // returned the message's full length so they should be equal. + ASSERT_NE(len, 0); + ASSERT_EQ(peeklen, len); + + for (struct nlmsghdr* hdr = reinterpret_cast<struct nlmsghdr*>(buf.data()); + NLMSG_OK(hdr, len); hdr = NLMSG_NEXT(hdr, len)) { + type = hdr->nlmsg_type; + } + } while (type != NLMSG_DONE && type != NLMSG_ERROR); +} + } // namespace } // namespace testing diff --git a/test/syscalls/linux/socket_netlink_util.cc b/test/syscalls/linux/socket_netlink_util.cc index 36b6560c2..fcb8f8a88 100644 --- a/test/syscalls/linux/socket_netlink_util.cc +++ b/test/syscalls/linux/socket_netlink_util.cc @@ -91,6 +91,13 @@ PosixError NetlinkRequestResponse( NLMSG_OK(hdr, len); hdr = NLMSG_NEXT(hdr, len)) { fn(hdr); type = hdr->nlmsg_type; + // Done should include an integer payload for dump_done_errno. + // See net/netlink/af_netlink.c:netlink_dump + // Some tools like the 'ip' tool check the minimum length of the + // NLMSG_DONE message. + if (type == NLMSG_DONE) { + EXPECT_GE(hdr->nlmsg_len, NLMSG_LENGTH(sizeof(int))); + } } } while (type != NLMSG_DONE && type != NLMSG_ERROR); |