diff options
| -rw-r--r-- | pkg/sentry/vfs/lock.go | 16 | ||||
| -rw-r--r-- | test/syscalls/linux/flock.cc | 54 |
2 files changed, 66 insertions, 4 deletions
diff --git a/pkg/sentry/vfs/lock.go b/pkg/sentry/vfs/lock.go index 6c7583a81..42666eebf 100644 --- a/pkg/sentry/vfs/lock.go +++ b/pkg/sentry/vfs/lock.go @@ -46,7 +46,13 @@ func (fl *FileLocks) LockBSD(uid fslock.UniqueID, t fslock.LockType, block fsloc if fl.bsd.LockRegion(uid, t, fslock.LockRange{0, fslock.LockEOF}, block) { return nil } - return syserror.ErrWouldBlock + + // Return an appropriate error for the unsuccessful lock attempt, depending on + // whether this is a blocking or non-blocking operation. + if block == nil { + return syserror.ErrWouldBlock + } + return syserror.ERESTARTSYS } // UnlockBSD releases a BSD-style lock on the entire file. @@ -66,7 +72,13 @@ func (fl *FileLocks) LockPOSIX(ctx context.Context, fd *FileDescription, uid fsl if fl.posix.LockRegion(uid, t, rng, block) { return nil } - return syserror.ErrWouldBlock + + // Return an appropriate error for the unsuccessful lock attempt, depending on + // whether this is a blocking or non-blocking operation. + if block == nil { + return syserror.ErrWouldBlock + } + return syserror.ERESTARTSYS } // UnlockPOSIX releases a POSIX-style lock on a file region. diff --git a/test/syscalls/linux/flock.cc b/test/syscalls/linux/flock.cc index 638a93979..549141cbb 100644 --- a/test/syscalls/linux/flock.cc +++ b/test/syscalls/linux/flock.cc @@ -185,7 +185,7 @@ TEST_F(FlockTest, TestMultipleHolderSharedExclusive) { ASSERT_THAT(flock(test_file_fd_.get(), LOCK_UN), SyscallSucceedsWithValue(0)); } -TEST_F(FlockTest, TestSharedLockFailExclusiveHolder) { +TEST_F(FlockTest, TestSharedLockFailExclusiveHolderNonblocking) { // This test will verify that a shared lock is denied while // someone holds an exclusive lock. ASSERT_THAT(flock(test_file_fd_.get(), LOCK_EX | LOCK_NB), @@ -203,7 +203,33 @@ TEST_F(FlockTest, TestSharedLockFailExclusiveHolder) { ASSERT_THAT(flock(test_file_fd_.get(), LOCK_UN), SyscallSucceedsWithValue(0)); } -TEST_F(FlockTest, TestExclusiveLockFailExclusiveHolder) { +void trivial_handler(int signum) {} + +TEST_F(FlockTest, TestSharedLockFailExclusiveHolderBlocking_NoRandomSave) { + const DisableSave ds; // Timing-related. + + // This test will verify that a shared lock is denied while + // someone holds an exclusive lock. + ASSERT_THAT(flock(test_file_fd_.get(), LOCK_EX | LOCK_NB), + SyscallSucceedsWithValue(0)); + + const FileDescriptor fd = + ASSERT_NO_ERRNO_AND_VALUE(Open(test_file_name_, O_RDWR)); + + // Register a signal handler for SIGALRM and set an alarm that will go off + // while blocking in the subsequent flock() call. This will interrupt flock() + // and cause it to return EINTR. + struct sigaction act = {}; + act.sa_handler = trivial_handler; + ASSERT_THAT(sigaction(SIGALRM, &act, NULL), SyscallSucceeds()); + ASSERT_THAT(ualarm(10000, 0), SyscallSucceeds()); + ASSERT_THAT(flock(fd.get(), LOCK_SH), SyscallFailsWithErrno(EINTR)); + + // Unlock + ASSERT_THAT(flock(test_file_fd_.get(), LOCK_UN), SyscallSucceedsWithValue(0)); +} + +TEST_F(FlockTest, TestExclusiveLockFailExclusiveHolderNonblocking) { // This test will verify that an exclusive lock is denied while // someone already holds an exclsuive lock. ASSERT_THAT(flock(test_file_fd_.get(), LOCK_EX | LOCK_NB), @@ -221,6 +247,30 @@ TEST_F(FlockTest, TestExclusiveLockFailExclusiveHolder) { ASSERT_THAT(flock(test_file_fd_.get(), LOCK_UN), SyscallSucceedsWithValue(0)); } +TEST_F(FlockTest, TestExclusiveLockFailExclusiveHolderBlocking_NoRandomSave) { + const DisableSave ds; // Timing-related. + + // This test will verify that an exclusive lock is denied while + // someone already holds an exclsuive lock. + ASSERT_THAT(flock(test_file_fd_.get(), LOCK_EX | LOCK_NB), + SyscallSucceedsWithValue(0)); + + const FileDescriptor fd = + ASSERT_NO_ERRNO_AND_VALUE(Open(test_file_name_, O_RDWR)); + + // Register a signal handler for SIGALRM and set an alarm that will go off + // while blocking in the subsequent flock() call. This will interrupt flock() + // and cause it to return EINTR. + struct sigaction act = {}; + act.sa_handler = trivial_handler; + ASSERT_THAT(sigaction(SIGALRM, &act, NULL), SyscallSucceeds()); + ASSERT_THAT(ualarm(10000, 0), SyscallSucceeds()); + ASSERT_THAT(flock(fd.get(), LOCK_EX), SyscallFailsWithErrno(EINTR)); + + // Unlock + ASSERT_THAT(flock(test_file_fd_.get(), LOCK_UN), SyscallSucceedsWithValue(0)); +} + TEST_F(FlockTest, TestMultipleHolderSharedExclusiveUpgrade) { // This test will verify that we cannot obtain an exclusive lock while // a shared lock is held by another descriptor, then verify that an upgrade |