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Fix potential BSD locking race. (#98)

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This commit is contained in:
Nuno Cruces
2024-06-12 20:41:51 +01:00
committed by GitHub
parent f7ac77027c
commit 3719692349
4 changed files with 12 additions and 3 deletions
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1
vfs/const.go
View File

@@ -51,6 +51,7 @@ const (
_IOERR_BEGIN_ATOMIC _ErrorCode = util.IOERR_BEGIN_ATOMIC
_IOERR_COMMIT_ATOMIC _ErrorCode = util.IOERR_COMMIT_ATOMIC
_IOERR_ROLLBACK_ATOMIC _ErrorCode = util.IOERR_ROLLBACK_ATOMIC
_BUSY_SNAPSHOT _ErrorCode = util.BUSY_SNAPSHOT
_CANTOPEN_FULLPATH _ErrorCode = util.CANTOPEN_FULLPATH
_CANTOPEN_ISDIR _ErrorCode = util.CANTOPEN_ISDIR
_READONLY_CANTINIT _ErrorCode = util.READONLY_CANTINIT

9
vfs/os_bsd.go
View File

@@ -29,5 +29,12 @@ func osReadLock(file *os.File, _ /*start*/, _ /*len*/ int64, _ /*timeout*/ time.
}
func osWriteLock(file *os.File, _ /*start*/, _ /*len*/ int64, _ /*timeout*/ time.Duration) _ErrorCode {
return osLock(file, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK)
rc := osLock(file, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK)
if rc == _BUSY {
// The documentation states the lock is upgraded by releasing the previous lock,
// then acquiring the new lock.
// This is a race, so return BUSY_SNAPSHOT to ensure the transaction is aborted.
return _BUSY_SNAPSHOT
}
return rc
}

2
vfs/os_unix_lock.go
View File

@@ -48,7 +48,7 @@ func osDowngradeLock(file *os.File, state LockLevel) _ErrorCode {
// In theory, the downgrade to a SHARED cannot fail because another
// process is holding an incompatible lock. If it does, this
// indicates that the other process is not following the locking
// protocol. If this happens, return _IOERR_RDLOCK. Returning
// protocol. If this happens, return IOERR_RDLOCK. Returning
// BUSY would confuse the upper layer.
return _IOERR_RDLOCK
}

3
vfs/shm_bsd.go
View File

@@ -128,10 +128,11 @@ func (s *vfsShm) shmOpen() (rc _ErrorCode) {
}
// Lock and truncate the file, if not readonly.
// The lock is only released by closing the file.
if s.readOnly {
rc = _READONLY_CANTINIT
} else {
if rc := osWriteLock(f, 0, 0, 0); rc != _OK {
if rc := osLock(f, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK); rc != _OK {
return rc
}
if err := f.Truncate(0); err != nil {