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Implement command GETNCNT for semctl.

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PiperOrigin-RevId: 341154192
This commit is contained in:
Jing Chen
2020-11-06 18:38:13 -08:00
committed by gVisor bot
parent 5288e19415
commit 3ac00fe9c3
4 changed files with 161 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/sentry/kernel/semaphore/semaphore.go
+28 -7
View File
@@ -103,6 +103,7 @@ type waiter struct {
waiterEntry
// value represents how much resource the waiter needs to wake up.
// The value is either 0 or negative.
value int16
ch chan struct{}
}
@@ -423,8 +424,7 @@ func (s *Set) GetPID(num int32, creds *auth.Credentials) (int32, error) {
return sem.pid, nil
}
// GetZeroWaiters returns number of waiters waiting for the sem to go to zero.
func (s *Set) GetZeroWaiters(num int32, creds *auth.Credentials) (uint16, error) {
func (s *Set) countWaiters(num int32, creds *auth.Credentials, pred func(w *waiter) bool) (uint16, error) {
s.mu.Lock()
defer s.mu.Unlock()
@@ -437,13 +437,27 @@ func (s *Set) GetZeroWaiters(num int32, creds *auth.Credentials) (uint16, error)
if sem == nil {
return 0, syserror.ERANGE
}
var semzcnt uint16
var cnt uint16
for w := sem.waiters.Front(); w != nil; w = w.Next() {
if w.value == 0 {
semzcnt++
if pred(w) {
cnt++
}
}
return semzcnt, nil
return cnt, nil
}
// CountZeroWaiters returns number of waiters waiting for the sem's value to increase.
func (s *Set) CountZeroWaiters(num int32, creds *auth.Credentials) (uint16, error) {
return s.countWaiters(num, creds, func(w *waiter) bool {
return w.value == 0
})
}
// CountNegativeWaiters returns number of waiters waiting for the sem to go to zero.
func (s *Set) CountNegativeWaiters(num int32, creds *auth.Credentials) (uint16, error) {
return s.countWaiters(num, creds, func(w *waiter) bool {
return w.value < 0
})
}
// ExecuteOps attempts to execute a list of operations to the set. It only
@@ -598,11 +612,18 @@ func (s *Set) destroy() {
}
}
func abs(val int16) int16 {
if val < 0 {
return -val
}
return val
}
// wakeWaiters goes over all waiters and checks which of them can be notified.
func (s *sem) wakeWaiters() {
// Note that this will release all waiters waiting for 0 too.
for w := s.waiters.Front(); w != nil; {
if s.value < w.value {
if s.value < abs(w.value) {
// Still blocked, skip it.
w = w.Next()
continue
pkg/sentry/syscalls/linux/linux64.go
+2 -2
View File
@@ -118,7 +118,7 @@ var AMD64 = &kernel.SyscallTable{
63: syscalls.Supported("uname", Uname),
64: syscalls.Supported("semget", Semget),
65: syscalls.PartiallySupported("semop", Semop, "Option SEM_UNDO not supported.", nil),
66: syscalls.PartiallySupported("semctl", Semctl, "Options IPC_INFO, SEM_INFO, SEM_STAT, SEM_STAT_ANY, GETNCNT not supported.", nil),
66: syscalls.PartiallySupported("semctl", Semctl, "Options IPC_INFO, SEM_INFO, SEM_STAT, SEM_STAT_ANY not supported.", nil),
67: syscalls.Supported("shmdt", Shmdt),
68: syscalls.ErrorWithEvent("msgget", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
69: syscalls.ErrorWithEvent("msgsnd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
@@ -619,7 +619,7 @@ var ARM64 = &kernel.SyscallTable{
188: syscalls.ErrorWithEvent("msgrcv", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
189: syscalls.ErrorWithEvent("msgsnd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
190: syscalls.Supported("semget", Semget),
191: syscalls.PartiallySupported("semctl", Semctl, "Options IPC_INFO, SEM_INFO, SEM_STAT, SEM_STAT_ANY, GETNCNT not supported.", nil),
191: syscalls.PartiallySupported("semctl", Semctl, "Options IPC_INFO, SEM_INFO, SEM_STAT, SEM_STAT_ANY not supported.", nil),
192: syscalls.ErrorWithEvent("semtimedop", syserror.ENOSYS, "", []string{"gvisor.dev/issue/137"}),
193: syscalls.PartiallySupported("semop", Semop, "Option SEM_UNDO not supported.", nil),
194: syscalls.PartiallySupported("shmget", Shmget, "Option SHM_HUGETLB is not supported.", nil),
pkg/sentry/syscalls/linux/sys_sem.go
+18 -5
View File
@@ -139,14 +139,17 @@ func Semctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
return 0, nil, err
case linux.GETZCNT:
v, err := getSemzcnt(t, id, num)
v, err := getZCnt(t, id, num)
return uintptr(v), nil, err
case linux.GETNCNT:
v, err := getNCnt(t, id, num)
return uintptr(v), nil, err
case linux.IPC_INFO,
linux.SEM_INFO,
linux.SEM_STAT,
linux.SEM_STAT_ANY,
linux.GETNCNT:
linux.SEM_STAT_ANY:
t.Kernel().EmitUnimplementedEvent(t)
fallthrough
@@ -262,12 +265,22 @@ func getPID(t *kernel.Task, id int32, num int32) (int32, error) {
return int32(tg.ID()), nil
}
func getSemzcnt(t *kernel.Task, id int32, num int32) (uint16, error) {
func getZCnt(t *kernel.Task, id int32, num int32) (uint16, error) {
r := t.IPCNamespace().SemaphoreRegistry()
set := r.FindByID(id)
if set == nil {
return 0, syserror.EINVAL
}
creds := auth.CredentialsFromContext(t)
return set.GetZeroWaiters(num, creds)
return set.CountZeroWaiters(num, creds)
}
func getNCnt(t *kernel.Task, id int32, num int32) (uint16, error) {
r := t.IPCNamespace().SemaphoreRegistry()
set := r.FindByID(id)
if set == nil {
return 0, syserror.EINVAL
}
creds := auth.CredentialsFromContext(t)
return set.CountNegativeWaiters(num, creds)
}
test/syscalls/linux/semaphore.cc
+113 -7
View File
@@ -543,14 +543,14 @@ TEST(SemaphoreTest, SemCtlIpcStat) {
SyscallFailsWithErrno(EACCES));
}
// Calls semctl(GETZCNT) until the returned value is >= target, an internal
// timeout expires, or semctl returns an error.
PosixErrorOr<int> WaitSemzcnt(int semid, int target) {
// Calls semctl(semid, 0, cmd) until the returned value is >= target, an
// internal timeout expires, or semctl returns an error.
PosixErrorOr<int> WaitSemctl(int semid, int target, int cmd) {
constexpr absl::Duration timeout = absl::Seconds(10);
const auto deadline = absl::Now() + timeout;
int semcnt = 0;
while (absl::Now() < deadline) {
semcnt = semctl(semid, 0, GETZCNT);
semcnt = semctl(semid, 0, cmd);
if (semcnt < 0) {
return PosixError(errno, "semctl(GETZCNT) failed");
}
@@ -594,7 +594,9 @@ TEST(SemaphoreTest, SemopGetzcnt) {
}
children.push_back(child_pid);
}
EXPECT_THAT(WaitSemzcnt(sem.get(), kLoops), IsPosixErrorOkAndHolds(kLoops));
EXPECT_THAT(WaitSemctl(sem.get(), kLoops, GETZCNT),
IsPosixErrorOkAndHolds(kLoops));
// Set semval to 0, which wakes up children that sleep on the semop.
ASSERT_THAT(semctl(sem.get(), 0, SETVAL, 0), SyscallSucceeds());
for (const auto& child_pid : children) {
@@ -625,7 +627,7 @@ TEST(SemaphoreTest, SemopGetzcntOnSetRemoval) {
_exit(0);
}
EXPECT_THAT(WaitSemzcnt(semid, 1), IsPosixErrorOkAndHolds(1));
EXPECT_THAT(WaitSemctl(semid, 1, GETZCNT), IsPosixErrorOkAndHolds(1));
// Remove the semaphore set, which fails the sleep semop.
ASSERT_THAT(semctl(semid, 0, IPC_RMID), SyscallSucceeds());
int status;
@@ -654,7 +656,8 @@ TEST(SemaphoreTest, SemopGetzcntOnSignal_NoRandomSave) {
TEST_PCHECK(semop(sem.get(), &buf, 1) < 0 && errno == EINTR);
_exit(0);
}
EXPECT_THAT(WaitSemzcnt(sem.get(), 1), IsPosixErrorOkAndHolds(1));
EXPECT_THAT(WaitSemctl(sem.get(), 1, GETZCNT), IsPosixErrorOkAndHolds(1));
// Send a signal to the child, which fails the sleep semop.
ASSERT_EQ(kill(child_pid, SIGHUP), 0);
@@ -667,6 +670,109 @@ TEST(SemaphoreTest, SemopGetzcntOnSignal_NoRandomSave) {
EXPECT_EQ(semctl(sem.get(), 0, GETZCNT), 0);
}
TEST(SemaphoreTest, SemopGetncnt) {
// Drop CAP_IPC_OWNER which allows us to bypass semaphore permissions.
ASSERT_NO_ERRNO(SetCapability(CAP_IPC_OWNER, false));
// Create a write only semaphore set.
AutoSem sem(semget(IPC_PRIVATE, 1, 0200 | IPC_CREAT));
ASSERT_THAT(sem.get(), SyscallSucceeds());
// No read permission to retrieve semzcnt.
EXPECT_THAT(semctl(sem.get(), 0, GETNCNT), SyscallFailsWithErrno(EACCES));
// Remove the calling thread's read permission.
struct semid_ds ds = {};
ds.sem_perm.uid = getuid();
ds.sem_perm.gid = getgid();
ds.sem_perm.mode = 0600;
ASSERT_THAT(semctl(sem.get(), 0, IPC_SET, &ds), SyscallSucceeds());
std::vector<pid_t> children;
struct sembuf buf = {};
buf.sem_num = 0;
buf.sem_op = -1;
constexpr size_t kLoops = 10;
for (auto i = 0; i < kLoops; i++) {
auto child_pid = fork();
if (child_pid == 0) {
TEST_PCHECK(RetryEINTR(semop)(sem.get(), &buf, 1) == 0);
_exit(0);
}
children.push_back(child_pid);
}
EXPECT_THAT(WaitSemctl(sem.get(), kLoops, GETNCNT),
IsPosixErrorOkAndHolds(kLoops));
// Set semval to 1, which wakes up children that sleep on the semop.
ASSERT_THAT(semctl(sem.get(), 0, SETVAL, kLoops), SyscallSucceeds());
for (const auto& child_pid : children) {
int status;
ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
}
EXPECT_EQ(semctl(sem.get(), 0, GETNCNT), 0);
}
TEST(SemaphoreTest, SemopGetncntOnSetRemoval) {
auto semid = semget(IPC_PRIVATE, 1, 0600 | IPC_CREAT);
ASSERT_THAT(semid, SyscallSucceeds());
ASSERT_EQ(semctl(semid, 0, GETNCNT), 0);
auto child_pid = fork();
if (child_pid == 0) {
struct sembuf buf = {};
buf.sem_num = 0;
buf.sem_op = -1;
// Ensure that wait will only unblock when the semaphore is removed. On
// EINTR retry it may race with deletion and return EINVAL
TEST_PCHECK(RetryEINTR(semop)(semid, &buf, 1) < 0 &&
(errno == EIDRM || errno == EINVAL));
_exit(0);
}
EXPECT_THAT(WaitSemctl(semid, 1, GETNCNT), IsPosixErrorOkAndHolds(1));
// Remove the semaphore set, which fails the sleep semop.
ASSERT_THAT(semctl(semid, 0, IPC_RMID), SyscallSucceeds());
int status;
ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
EXPECT_THAT(semctl(semid, 0, GETNCNT), SyscallFailsWithErrno(EINVAL));
}
TEST(SemaphoreTest, SemopGetncntOnSignal_NoRandomSave) {
AutoSem sem(semget(IPC_PRIVATE, 1, 0600 | IPC_CREAT));
ASSERT_THAT(sem.get(), SyscallSucceeds());
ASSERT_EQ(semctl(sem.get(), 0, GETNCNT), 0);
// Saving will cause semop() to be spuriously interrupted.
DisableSave ds;
auto child_pid = fork();
if (child_pid == 0) {
TEST_PCHECK(signal(SIGHUP, [](int sig) -> void {}) != SIG_ERR);
struct sembuf buf = {};
buf.sem_num = 0;
buf.sem_op = -1;
TEST_PCHECK(semop(sem.get(), &buf, 1) < 0 && errno == EINTR);
_exit(0);
}
EXPECT_THAT(WaitSemctl(sem.get(), 1, GETNCNT), IsPosixErrorOkAndHolds(1));
// Send a signal to the child, which fails the sleep semop.
ASSERT_EQ(kill(child_pid, SIGHUP), 0);
ds.reset();
int status;
ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
EXPECT_EQ(semctl(sem.get(), 0, GETNCNT), 0);
}
} // namespace
} // namespace testing
} // namespace gvisor