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Clears O_CREATE when re-opening a file to set flags (#1458)

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Signed-off-by: Adrian Cole <adrian@tetrate.io>
This commit is contained in:
Crypt Keeper
2023-05-12 14:35:17 +08:00
committed by GitHub
parent 13e38966b6
commit cd5c9ed37c
4 changed files with 44 additions and 12 deletions
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2
imports/wasi_snapshot_preview1/fs.go
View File

@@ -205,7 +205,7 @@ func fdFdstatGetFn(_ context.Context, mod api.Module, params []uint64) syscall.E
if f.File.IsNonblock() {
fdflags |= wasip1.FD_NONBLOCK
}
} else if f.File.AccessMode() != syscall.O_RDONLY {
} else if f.IsAppend() {
fdflags |= wasip1.FD_APPEND
}

26
imports/wasi_snapshot_preview1/fs_test.go
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@@ -250,7 +250,8 @@ func Test_fdFdstatGet(t *testing.T) {
stdin.File = stdinFile
fileFD, errno := fsc.OpenFile(preopen, file, os.O_RDONLY, 0)
// Make this file writeable, to ensure flags read-back correctly.
fileFD, errno := fsc.OpenFile(preopen, file, os.O_RDWR|os.O_APPEND, 0)
require.EqualErrno(t, 0, errno)
dirFD, errno := fsc.OpenFile(preopen, dir, os.O_RDONLY, 0)
@@ -325,13 +326,13 @@ func Test_fdFdstatGet(t *testing.T) {
fd: fileFD,
expectedMemory: []byte{
4, 0, // fs_filetype
0, 0, 0, 0, 0, 0, // fs_flags
1, 0, 0, 0, 0, 0, // fs_flags
0xff, 0x1, 0xe0, 0x8, 0x0, 0x0, 0x0, 0x0, // fs_rights_base
0, 0, 0, 0, 0, 0, 0, 0, // fs_rights_inheriting
},
expectedLog: `
==> wasi_snapshot_preview1.fd_fdstat_get(fd=4)
<== (stat={filetype=REGULAR_FILE,fdflags=,fs_rights_base=FD_DATASYNC|FD_READ|FD_SEEK|FDSTAT_SET_FLAGS|FD_SYNC|FD_TELL|FD_WRITE|FD_ADVISE|FD_ALLOCATE,fs_rights_inheriting=},errno=ESUCCESS)
<== (stat={filetype=REGULAR_FILE,fdflags=APPEND,fs_rights_base=FD_DATASYNC|FD_READ|FD_SEEK|FDSTAT_SET_FLAGS|FD_SYNC|FD_TELL|FD_WRITE|FD_ADVISE|FD_ALLOCATE,fs_rights_inheriting=},errno=ESUCCESS)
`,
},
{
@@ -481,11 +482,6 @@ func Test_fdFdstatGet_StdioNonblock(t *testing.T) {
func Test_fdFdstatSetFlags(t *testing.T) {
tmpDir := t.TempDir() // open before loop to ensure no locking problems.
const fileName = "file.txt"
// Create the target file.
realPath := joinPath(tmpDir, fileName)
require.NoError(t, os.WriteFile(realPath, []byte("0123456789"), 0o600))
stdinR, stdinW := openPipe(t)
defer closePipe(stdinR, stdinW)
@@ -505,8 +501,18 @@ func Test_fdFdstatSetFlags(t *testing.T) {
preopen := fsc.RootFS()
defer r.Close(testCtx)
// First, open it with O_APPEND.
fd, errno := fsc.OpenFile(preopen, fileName, os.O_RDWR|os.O_APPEND, 0)
// First, O_CREATE the file with O_APPEND. We use O_EXCL because that
// triggers an EEXIST error if called a second time with O_CREATE. Our
// logic should clear O_CREATE preventing this.
const fileName = "file.txt"
// Create the target file.
fd, errno := fsc.OpenFile(preopen, fileName, os.O_RDWR|os.O_APPEND|os.O_CREATE|syscall.O_EXCL, 0o600)
require.EqualErrno(t, 0, errno)
// Write the initial text to the file.
f, ok := fsc.LookupFile(fd)
require.True(t, ok)
_, errno = f.File.Write([]byte("0123456789"))
require.EqualErrno(t, 0, errno)
writeWazero := func() {

10
internal/sys/fs.go
View File

@@ -255,6 +255,11 @@ type cachedStat struct {
Ino uint64
}
// IsAppend returns true if the file is open with syscall.O_APPEND.
func (f *FileEntry) IsAppend() bool {
return f.openFlag&syscall.O_APPEND != 0
}
// Inode returns the cached inode from of platform.Stat_t or an error if it
// couldn't be retrieved.
func (f *FileEntry) Inode() (ino uint64, errno syscall.Errno) {
@@ -462,6 +467,8 @@ func (c *FSContext) ChangeOpenFlag(fd int32, flag int) syscall.Errno {
return errno
} else if isDir {
return syscall.EISDIR
} else if flag&syscall.O_APPEND == f.openFlag&syscall.O_APPEND {
return 0 // don't re-open
}
if flag&syscall.O_APPEND != 0 {
@@ -470,6 +477,9 @@ func (c *FSContext) ChangeOpenFlag(fd int32, flag int) syscall.Errno {
f.openFlag &= ^syscall.O_APPEND
}
// Clear any create flag, as we are re-opening, not re-creating.
f.openFlag &= ^syscall.O_CREAT
// Changing the flag while opening is not really supported well in Go. Even when using
// syscall package, the feasibility of doing so really depends on the platform. For examples:
//

18
internal/sys/fs_test.go
View File

@@ -329,7 +329,7 @@ func TestFSContext_ChangeOpenFlag(t *testing.T) {
tmpDir := t.TempDir()
dirFs := sysfs.NewDirFS(tmpDir)
const fileName = "dir"
const fileName = "file"
require.NoError(t, os.WriteFile(path.Join(tmpDir, fileName), []byte("0123456789"), 0o600))
c := Context{}
@@ -360,6 +360,22 @@ func TestFSContext_ChangeOpenFlag(t *testing.T) {
f2, ok := fsc.openedFiles.Lookup(fd)
require.True(t, ok)
require.Equal(t, f2.openFlag&syscall.O_APPEND, 0)
t.Run("create exclusive", func(t *testing.T) {
// O_EXCL triggers an EEXIST error if called a second time with
// O_CREATE. This test proves the internal logic clears O_CREATE on
// re-open.
const fileName = "exclusive"
fd, errno := fsc.OpenFile(dirFs, fileName, os.O_RDWR|os.O_CREATE|syscall.O_EXCL, 0o600)
require.EqualErrno(t, 0, errno)
errno = fsc.ChangeOpenFlag(fd, syscall.O_APPEND)
require.EqualErrno(t, 0, errno)
f1, ok := fsc.openedFiles.Lookup(fd)
require.True(t, ok)
require.Equal(t, f1.openFlag&syscall.O_APPEND, syscall.O_APPEND)
})
}
func TestStdio(t *testing.T) {