mirrors/versitygw
1
0
Fork 0
mirror of https://github.com/versity/versitygw.git synced 2025-12-23 05:05:16 +00:00
Code Issues Packages Projects Releases Wiki Activity

Fix O_TMPFILE Linkat race.

Browse Source
This commit is contained in:
Ondrej Palkovsky
2025-08-07 18:20:09 +02:00
parent 742cebb5e5
commit e62337f055
1 changed files with 27 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

45
backend/posix/with_otmpfile.go
View File

@@ -26,6 +26,7 @@ import (
"path/filepath"
"strconv"
"syscall"
"time"
"github.com/versity/versitygw/auth"
"github.com/versity/versitygw/backend"
@@ -165,14 +166,10 @@ func (tmp *tmpfile) link() error {
// of last upload completed wins and is not some combination of writes
// from simultaneous uploads.
objPath := filepath.Join(tmp.bucket, tmp.objname)
err := os.Remove(objPath)
if err != nil && !errors.Is(err, fs.ErrNotExist) {
return fmt.Errorf("remove stale path: %w", err)
}
dir := filepath.Dir(objPath)
err = backend.MkdirAll(dir, tmp.uid, tmp.gid, tmp.needsChown, tmp.newDirPerm)
err := backend.MkdirAll(dir, tmp.uid, tmp.gid, tmp.needsChown, tmp.newDirPerm)
if err != nil {
return fmt.Errorf("make parent dir: %w", err)
}
@@ -194,21 +191,33 @@ func (tmp *tmpfile) link() error {
}
defer dirf.Close()
for {
err = unix.Linkat(int(procdir.Fd()), filepath.Base(tmp.f.Name()),
int(dirf.Fd()), filepath.Base(objPath), unix.AT_SYMLINK_FOLLOW)
if errors.Is(err, syscall.EEXIST) {
err := os.Remove(objPath)
if err != nil && !errors.Is(err, fs.ErrNotExist) {
return fmt.Errorf("remove stale path: %w", err)
err = unix.Linkat(int(procdir.Fd()), filepath.Base(tmp.f.Name()),
int(dirf.Fd()), filepath.Base(objPath), unix.AT_SYMLINK_FOLLOW)
if errors.Is(err, syscall.EEXIST) {
// Linkat cannot overwrite files; we will allocate a temporary file, Linkat to it and then Renameat it
// to avoid potential race condition
retries := 1
for {
tmpName := fmt.Sprintf(".%s.sgwtmp.%d", filepath.Base(objPath), time.Now().UnixNano())
err := unix.Linkat(int(procdir.Fd()), filepath.Base(tmp.f.Name()),
int(dirf.Fd()), tmpName, unix.AT_SYMLINK_FOLLOW)
if errors.Is(err, syscall.EEXIST) && retries < 3 {
retries += 1
continue
}
continue
if err != nil {
return fmt.Errorf("cannot find free temporary file: %w", err)
}
err = unix.Renameat(int(dirf.Fd()), tmpName, int(dirf.Fd()), filepath.Base(objPath))
if err != nil {
return fmt.Errorf("Overwriting renameat failed: %w", err)
}
break
}
if err != nil {
return fmt.Errorf("link tmpfile (fd %q as %q): %w",
filepath.Base(tmp.f.Name()), objPath, err)
}
break
} else if err != nil {
return fmt.Errorf("link tmpfile (fd %q as %q): %w",
filepath.Base(tmp.f.Name()), objPath, err)
}
err = tmp.f.Close()