Merge pull request #6171 from sudo-sturbia:msgqueue/syscalls2

PiperOrigin-RevId: 388497055

2 files changed, 574 insertions, 0 deletions

diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 3383495d0..7129a797b 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -4172,9 +4172,11 @@ cc_binary(
     srcs = ["msgqueue.cc"],
     linkstatic = 1,
     deps = [
+        "//test/util:capability_util",
         "//test/util:temp_path",
         "//test/util:test_main",
         "//test/util:test_util",
+        "@com_google_absl//absl/time",
     ],
 )
 
diff --git a/test/syscalls/linux/msgqueue.cc b/test/syscalls/linux/msgqueue.cc
index 2409de7e8..837e913d9 100644
--- a/test/syscalls/linux/msgqueue.cc
+++ b/test/syscalls/linux/msgqueue.cc
@@ -12,10 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <errno.h>
 #include <sys/ipc.h>
 #include <sys/msg.h>
 #include <sys/types.h>
 
+#include "absl/time/clock.h"
+#include "test/util/capability_util.h"
 #include "test/util/temp_path.h"
 #include "test/util/test_util.h"
 
@@ -23,6 +26,10 @@ namespace gvisor {
 namespace testing {
 namespace {
 
+constexpr int msgMax = 8192;   // Max size for message in bytes.
+constexpr int msgMni = 32000;  // Max number of identifiers.
+constexpr int msgMnb = 16384;  // Default max size of message queue in bytes.
+
 // Queue is a RAII class used to automatically clean message queues.
 class Queue {
  public:
@@ -46,6 +53,25 @@ class Queue {
   int id_ = -1;
 };
 
+// Default size for messages.
+constexpr size_t msgSize = 50;
+
+// msgbuf is a simple buffer using to send and receive text messages for
+// testing purposes.
+struct msgbuf {
+  int64_t mtype;
+  char mtext[msgSize];
+};
+
+bool operator==(msgbuf& a, msgbuf& b) {
+  for (size_t i = 0; i < msgSize; i++) {
+    if (a.mtext[i] != b.mtext[i]) {
+      return false;
+    }
+  }
+  return a.mtype == b.mtype;
+}
+
 // Test simple creation and retrieval for msgget(2).
 TEST(MsgqueueTest, MsgGet) {
   const TempPath keyfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
@@ -82,6 +108,552 @@ TEST(MsgqueueTest, MsgGetIpcPrivate) {
   EXPECT_NE(queue1.get(), queue2.get());
 }
 
+// Test simple msgsnd and msgrcv.
+TEST(MsgqueueTest, MsgOpSimple) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf buf{1, "A message."};
+  msgbuf rcv;
+
+  ASSERT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+              SyscallSucceeds());
+
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(buf.mtext) + 1, 0, 0),
+              SyscallSucceedsWithValue(sizeof(buf.mtext)));
+  EXPECT_TRUE(buf == rcv);
+}
+
+// Test msgsnd and msgrcv of an empty message.
+TEST(MsgqueueTest, MsgOpEmpty) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf buf{1, ""};
+  msgbuf rcv;
+
+  ASSERT_THAT(msgsnd(queue.get(), &buf, 0, 0), SyscallSucceeds());
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(buf.mtext) + 1, 0, 0),
+              SyscallSucceedsWithValue(0));
+}
+
+// Test truncation of message with MSG_NOERROR flag.
+TEST(MsgqueueTest, MsgOpTruncate) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf buf{1, ""};
+  msgbuf rcv;
+
+  ASSERT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+              SyscallSucceeds());
+
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(buf.mtext) - 1, 0, MSG_NOERROR),
+              SyscallSucceedsWithValue(sizeof(buf.mtext) - 1));
+}
+
+// Test msgsnd and msgrcv using invalid arguments.
+TEST(MsgqueueTest, MsgOpInvalidArgs) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf buf{1, ""};
+
+  EXPECT_THAT(msgsnd(-1, &buf, 0, 0), SyscallFailsWithErrno(EINVAL));
+  EXPECT_THAT(msgsnd(queue.get(), &buf, -1, 0), SyscallFailsWithErrno(EINVAL));
+
+  buf.mtype = -1;
+  EXPECT_THAT(msgsnd(queue.get(), &buf, 1, 0), SyscallFailsWithErrno(EINVAL));
+
+  EXPECT_THAT(msgrcv(-1, &buf, 1, 0, 0), SyscallFailsWithErrno(EINVAL));
+  EXPECT_THAT(msgrcv(queue.get(), &buf, -1, 0, 0),
+              SyscallFailsWithErrno(EINVAL));
+}
+
+// Test non-blocking msgrcv with an empty queue.
+TEST(MsgqueueTest, MsgOpNoMsg) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf rcv;
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(rcv.mtext) + 1, 0, IPC_NOWAIT),
+              SyscallFailsWithErrno(ENOMSG));
+}
+
+// Test non-blocking msgrcv with a non-empty queue, but no messages of wanted
+// type.
+TEST(MsgqueueTest, MsgOpNoMsgType) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf buf{1, ""};
+  ASSERT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+              SyscallSucceeds());
+
+  EXPECT_THAT(msgrcv(queue.get(), &buf, sizeof(buf.mtext) + 1, 2, IPC_NOWAIT),
+              SyscallFailsWithErrno(ENOMSG));
+}
+
+// Test msgrcv with a larger size message than wanted, and truncation disabled.
+TEST(MsgqueueTest, MsgOpTooBig) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf buf{1, ""};
+  ASSERT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+              SyscallSucceeds());
+
+  EXPECT_THAT(msgrcv(queue.get(), &buf, sizeof(buf.mtext) - 1, 0, 0),
+              SyscallFailsWithErrno(E2BIG));
+}
+
+// Test receiving messages based on type.
+TEST(MsgqueueTest, MsgRcvType) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  // Send messages in an order and receive them in reverse, based on type,
+  // which shouldn't block.
+  std::map<int64_t, msgbuf> typeToBuf = {
+      {1, msgbuf{1, "Message 1."}}, {2, msgbuf{2, "Message 2."}},
+      {3, msgbuf{3, "Message 3."}}, {4, msgbuf{4, "Message 4."}},
+      {5, msgbuf{5, "Message 5."}}, {6, msgbuf{6, "Message 6."}},
+      {7, msgbuf{7, "Message 7."}}, {8, msgbuf{8, "Message 8."}},
+      {9, msgbuf{9, "Message 9."}}};
+
+  for (auto const& [type, buf] : typeToBuf) {
+    ASSERT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+                SyscallSucceeds());
+  }
+
+  for (int64_t i = typeToBuf.size(); i > 0; i--) {
+    msgbuf rcv;
+    EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(typeToBuf[i].mtext) + 1, i, 0),
+                SyscallSucceedsWithValue(sizeof(typeToBuf[i].mtext)));
+    EXPECT_TRUE(typeToBuf[i] == rcv);
+  }
+}
+
+// Test using MSG_EXCEPT to receive a different-type message.
+TEST(MsgqueueTest, MsgExcept) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  std::map<int64_t, msgbuf> typeToBuf = {
+      {1, msgbuf{1, "Message 1."}},
+      {2, msgbuf{2, "Message 2."}},
+  };
+
+  for (auto const& [type, buf] : typeToBuf) {
+    ASSERT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+                SyscallSucceeds());
+  }
+
+  for (int64_t i = typeToBuf.size(); i > 0; i--) {
+    msgbuf actual = typeToBuf[i == 1 ? 2 : 1];
+    msgbuf rcv;
+
+    EXPECT_THAT(
+        msgrcv(queue.get(), &rcv, sizeof(actual.mtext) + 1, i, MSG_EXCEPT),
+        SyscallSucceedsWithValue(sizeof(actual.mtext)));
+    EXPECT_TRUE(actual == rcv);
+  }
+}
+
+// Test msgrcv with a negative type.
+TEST(MsgqueueTest, MsgRcvTypeNegative) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  //  When msgtyp is negative, msgrcv returns the first message with mtype less
+  //  than or equal to the absolute value.
+  msgbuf buf{2, "A message."};
+  msgbuf rcv;
+
+  ASSERT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+              SyscallSucceeds());
+
+  // Nothing is less than or equal to 1.
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(buf.mtext) + 1, -1, IPC_NOWAIT),
+              SyscallFailsWithErrno(ENOMSG));
+
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(buf.mtext) + 1, -3, 0),
+              SyscallSucceedsWithValue(sizeof(buf.mtext)));
+  EXPECT_TRUE(buf == rcv);
+}
+
+// Test permission-related failure scenarios.
+TEST(MsgqueueTest, MsgOpPermissions) {
+  AutoCapability cap(CAP_IPC_OWNER, false);
+
+  Queue queue(msgget(IPC_PRIVATE, 0000));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf buf{1, ""};
+
+  EXPECT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+              SyscallFailsWithErrno(EACCES));
+  EXPECT_THAT(msgrcv(queue.get(), &buf, sizeof(buf.mtext), 0, 0),
+              SyscallFailsWithErrno(EACCES));
+}
+
+// Test limits for messages and queues.
+TEST(MsgqueueTest, MsgOpLimits) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf buf{1, "A message."};
+
+  // Limit for one message.
+  EXPECT_THAT(msgsnd(queue.get(), &buf, msgMax + 1, 0),
+              SyscallFailsWithErrno(EINVAL));
+
+  // Limit for queue.
+  // Use a buffer with the maximum mount of bytes that can be transformed to
+  // make it easier to exhaust the queue limit.
+  struct msgmax {
+    int64_t mtype;
+    char mtext[msgMax];
+  };
+
+  msgmax limit{1, ""};
+  for (size_t i = 0, msgCount = msgMnb / msgMax; i < msgCount; i++) {
+    EXPECT_THAT(msgsnd(queue.get(), &limit, sizeof(limit.mtext), 0),
+                SyscallSucceeds());
+  }
+  EXPECT_THAT(msgsnd(queue.get(), &limit, sizeof(limit.mtext), IPC_NOWAIT),
+              SyscallFailsWithErrno(EAGAIN));
+}
+
+// MsgCopySupported returns true if MSG_COPY is supported.
+bool MsgCopySupported() {
+  // msgrcv(2) man page states that MSG_COPY flag is available only if the
+  // kernel was built with the CONFIG_CHECKPOINT_RESTORE option. If MSG_COPY
+  // is used when the kernel was configured without the option, msgrcv produces
+  // a ENOSYS error.
+  // To avoid test failure, we perform a small test using msgrcv, and skip the
+  // test if errno == ENOSYS. This means that the test will always run on
+  // gVisor, but may be skipped on native linux.
+
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+
+  msgbuf buf{1, "Test message."};
+  msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0);
+
+  return !(msgrcv(queue.get(), &buf, sizeof(buf.mtext) + 1, 0,
+                  MSG_COPY | IPC_NOWAIT) == -1 &&
+           errno == ENOSYS);
+}
+
+// Test msgrcv using MSG_COPY.
+TEST(MsgqueueTest, MsgCopy) {
+  SKIP_IF(!MsgCopySupported());
+
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf bufs[5] = {
+      msgbuf{1, "Message 1."}, msgbuf{2, "Message 2."}, msgbuf{3, "Message 3."},
+      msgbuf{4, "Message 4."}, msgbuf{5, "Message 5."},
+  };
+
+  for (auto& buf : bufs) {
+    ASSERT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+                SyscallSucceeds());
+  }
+
+  // Receive a copy of the messages.
+  for (size_t i = 0, size = sizeof(bufs) / sizeof(bufs[0]); i < size; i++) {
+    msgbuf buf = bufs[i];
+    msgbuf rcv;
+    EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(buf.mtext) + 1, i,
+                       MSG_COPY | IPC_NOWAIT),
+                SyscallSucceedsWithValue(sizeof(buf.mtext)));
+    EXPECT_TRUE(buf == rcv);
+  }
+
+  // Re-receive the messages normally.
+  for (auto& buf : bufs) {
+    msgbuf rcv;
+    EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(buf.mtext) + 1, 0, 0),
+                SyscallSucceedsWithValue(sizeof(buf.mtext)));
+    EXPECT_TRUE(buf == rcv);
+  }
+}
+
+// Test msgrcv using MSG_COPY with invalid arguments.
+TEST(MsgqueueTest, MsgCopyInvalidArgs) {
+  SKIP_IF(!MsgCopySupported());
+
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf rcv;
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, msgSize, 1, MSG_COPY),
+              SyscallFailsWithErrno(EINVAL));
+
+  EXPECT_THAT(
+      msgrcv(queue.get(), &rcv, msgSize, 5, MSG_COPY | MSG_EXCEPT | IPC_NOWAIT),
+      SyscallFailsWithErrno(EINVAL));
+}
+
+// Test msgrcv using MSG_COPY with invalid indices.
+TEST(MsgqueueTest, MsgCopyInvalidIndex) {
+  SKIP_IF(!MsgCopySupported());
+
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf rcv;
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, msgSize, -3, MSG_COPY | IPC_NOWAIT),
+              SyscallFailsWithErrno(ENOMSG));
+
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, msgSize, 5, MSG_COPY | IPC_NOWAIT),
+              SyscallFailsWithErrno(ENOMSG));
+}
+
+// Test msgrcv (most probably) blocking on an empty queue.
+TEST(MsgqueueTest, MsgRcvBlocking) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf buf{1, "A message."};
+
+  const pid_t child_pid = fork();
+  if (child_pid == 0) {
+    msgbuf rcv;
+    TEST_PCHECK(RetryEINTR(msgrcv)(queue.get(), &rcv, sizeof(buf.mtext) + 1, 0,
+                                   0) == sizeof(buf.mtext) &&
+                buf == rcv);
+    _exit(0);
+  }
+
+  // Sleep to try and make msgrcv block before sending a message.
+  absl::SleepFor(absl::Milliseconds(150));
+
+  EXPECT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+              SyscallSucceeds());
+
+  int status;
+  ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0),
+              SyscallSucceedsWithValue(child_pid));
+  EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+}
+
+// Test msgrcv (most probably) waiting for a specific-type message.
+TEST(MsgqueueTest, MsgRcvTypeBlocking) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  msgbuf bufs[5] = {{1, "A message."},
+                    {1, "A message."},
+                    {1, "A message."},
+                    {1, "A message."},
+                    {2, "A different message."}};
+
+  const pid_t child_pid = fork();
+  if (child_pid == 0) {
+    msgbuf buf = bufs[4];  // Buffer that should be received.
+    msgbuf rcv;
+    TEST_PCHECK(RetryEINTR(msgrcv)(queue.get(), &rcv, sizeof(buf.mtext) + 1, 2,
+                                   0) == sizeof(buf.mtext) &&
+                buf == rcv);
+    _exit(0);
+  }
+
+  // Sleep to try and make msgrcv block before sending messages.
+  absl::SleepFor(absl::Milliseconds(150));
+
+  // Send all buffers in order, only last one should be received.
+  for (auto& buf : bufs) {
+    EXPECT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+                SyscallSucceeds());
+  }
+
+  int status;
+  ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0),
+              SyscallSucceedsWithValue(child_pid));
+  EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+}
+
+// Test msgsnd (most probably) blocking on a full queue.
+TEST(MsgqueueTest, MsgSndBlocking) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  // Use a buffer with the maximum mount of bytes that can be transformed to
+  // make it easier to exhaust the queue limit.
+  struct msgmax {
+    int64_t mtype;
+    char mtext[msgMax];
+  };
+
+  msgmax buf{1, ""};  // Has max amount of bytes.
+
+  const size_t msgCount = msgMnb / msgMax;  // Number of messages that can be
+                                            // sent without blocking.
+
+  const pid_t child_pid = fork();
+  if (child_pid == 0) {
+    // Fill the queue.
+    for (size_t i = 0; i < msgCount; i++) {
+      TEST_PCHECK(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0) == 0);
+    }
+
+    // Next msgsnd should block.
+    TEST_PCHECK(RetryEINTR(msgsnd)(queue.get(), &buf, sizeof(buf.mtext), 0) ==
+                0);
+    _exit(0);
+  }
+
+  // To increase the chance of the last msgsnd blocking before doing a msgrcv,
+  // we use MSG_COPY option to copy the last index in the queue. As long as
+  // MSG_COPY fails, the queue hasn't yet been filled. When MSG_COPY succeeds,
+  // the queue is filled, and most probably, a blocking msgsnd has been made.
+  msgmax rcv;
+  while (msgrcv(queue.get(), &rcv, msgMax, msgCount - 1,
+                MSG_COPY | IPC_NOWAIT) == -1 &&
+         errno == ENOMSG) {
+  }
+
+  // Delay a bit more for the blocking msgsnd.
+  absl::SleepFor(absl::Milliseconds(100));
+
+  EXPECT_THAT(msgrcv(queue.get(), &rcv, sizeof(buf.mtext), 0, 0),
+              SyscallSucceedsWithValue(sizeof(buf.mtext)));
+
+  int status;
+  ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0),
+              SyscallSucceedsWithValue(child_pid));
+  EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+}
+
+// Test removing a queue while a blocking msgsnd is executing.
+TEST(MsgqueueTest, MsgSndRmWhileBlocking) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  // Use a buffer with the maximum mount of bytes that can be transformed to
+  // make it easier to exhaust the queue limit.
+  struct msgmax {
+    int64_t mtype;
+    char mtext[msgMax];
+  };
+
+  const size_t msgCount = msgMnb / msgMax;  // Number of messages that can be
+                                            // sent without blocking.
+  const pid_t child_pid = fork();
+  if (child_pid == 0) {
+    // Fill the queue.
+    msgmax buf{1, ""};
+    for (size_t i = 0; i < msgCount; i++) {
+      EXPECT_THAT(msgsnd(queue.get(), &buf, sizeof(buf.mtext), 0),
+                  SyscallSucceeds());
+    }
+
+    // Next msgsnd should block. Because we're repeating on EINTR, msgsnd may
+    // race with msgctl(IPC_RMID) and return EINVAL.
+    TEST_PCHECK(RetryEINTR(msgsnd)(queue.get(), &buf, sizeof(buf.mtext), 0) ==
+                    -1 &&
+                (errno == EIDRM || errno == EINVAL));
+    _exit(0);
+  }
+
+  // Similar to MsgSndBlocking, we do this to increase the chance of msgsnd
+  // blocking before removing the queue.
+  msgmax rcv;
+  while (msgrcv(queue.get(), &rcv, msgMax, msgCount - 1,
+                MSG_COPY | IPC_NOWAIT) == -1 &&
+         errno == ENOMSG) {
+  }
+  absl::SleepFor(absl::Milliseconds(100));
+
+  EXPECT_THAT(msgctl(queue.release(), IPC_RMID, nullptr), SyscallSucceeds());
+
+  int status;
+  ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0),
+              SyscallSucceedsWithValue(child_pid));
+  EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+}
+
+// Test removing a queue while a blocking msgrcv is executing.
+TEST(MsgqueueTest, MsgRcvRmWhileBlocking) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  const pid_t child_pid = fork();
+  if (child_pid == 0) {
+    // Because we're repeating on EINTR, msgsnd may race with msgctl(IPC_RMID)
+    // and return EINVAL.
+    msgbuf rcv;
+    TEST_PCHECK(RetryEINTR(msgrcv)(queue.get(), &rcv, 1, 2, 0) == -1 &&
+                (errno == EIDRM || errno == EINVAL));
+    _exit(0);
+  }
+
+  // Sleep to try and make msgrcv block before sending messages.
+  absl::SleepFor(absl::Milliseconds(150));
+
+  EXPECT_THAT(msgctl(queue.release(), IPC_RMID, nullptr), SyscallSucceeds());
+
+  int status;
+  ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0),
+              SyscallSucceedsWithValue(child_pid));
+  EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+}
+
+// Test a collection of msgsnd/msgrcv operations in different processes.
+TEST(MsgqueueTest, MsgOpGeneral) {
+  Queue queue(msgget(IPC_PRIVATE, 0600));
+  ASSERT_THAT(queue.get(), SyscallSucceeds());
+
+  // Create 50 sending, and 50 receiving processes. There are only 5 messages to
+  // be sent and received, each with a different type. All messages will be sent
+  // and received equally (10 of each.) By the end of the test all processes
+  // should unblock and return normally.
+  const size_t msgCount = 5;
+  std::map<int64_t, msgbuf> typeToBuf = {{1, msgbuf{1, "Message 1."}},
+                                         {2, msgbuf{2, "Message 2."}},
+                                         {3, msgbuf{3, "Message 3."}},
+                                         {4, msgbuf{4, "Message 4."}},
+                                         {5, msgbuf{5, "Message 5."}}};
+
+  std::vector<pid_t> children;
+
+  const size_t pCount = 50;
+  for (size_t i = 1; i <= pCount; i++) {
+    const pid_t child_pid = fork();
+    if (child_pid == 0) {
+      msgbuf buf = typeToBuf[(i % msgCount) + 1];
+      msgbuf rcv;
+      TEST_PCHECK(RetryEINTR(msgrcv)(queue.get(), &rcv, sizeof(buf.mtext) + 1,
+                                     (i % msgCount) + 1,
+                                     0) == sizeof(buf.mtext) &&
+                  buf == rcv);
+      _exit(0);
+    }
+    children.push_back(child_pid);
+  }
+
+  for (size_t i = 1; i <= pCount; i++) {
+    const pid_t child_pid = fork();
+    if (child_pid == 0) {
+      msgbuf buf = typeToBuf[(i % msgCount) + 1];
+      TEST_PCHECK(RetryEINTR(msgsnd)(queue.get(), &buf, sizeof(buf.mtext), 0) ==
+                  0);
+      _exit(0);
+    }
+    children.push_back(child_pid);
+  }
+
+  for (auto const& pid : children) {
+    int status;
+    ASSERT_THAT(RetryEINTR(waitpid)(pid, &status, 0),
+                SyscallSucceedsWithValue(pid));
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+}
+
 }  // namespace
 }  // namespace testing
 }  // namespace gvisor