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fusefrontend: allow_other: close race between symlink and chown 

Fixes the same problem as described in 72b975867a,
except for symlinks instead of device nodes.
This commit is contained in:
Sebastian Lackner 2017-11-28 01:02:11 +01:00 committed by rfjakob
parent 5a56810603
commit ad2720e0f9
1 changed files with 10 additions and 11 deletions
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21
internal/fusefrontend/fs.go
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@ -427,22 +427,20 @@ func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (co
if err != nil { if err != nil {
return fuse.ToStatus(err) return fuse.ToStatus(err)
} }
dirfd, err := os.Open(filepath.Dir(cPath))
if err != nil {
return fuse.ToStatus(err)
}
defer dirfd.Close()
var cTarget string = target var cTarget string = target
if !fs.args.PlaintextNames { if !fs.args.PlaintextNames {
// Symlinks are encrypted like file contents (GCM) and base64-encoded // Symlinks are encrypted like file contents (GCM) and base64-encoded
cBinTarget := fs.contentEnc.EncryptBlock([]byte(target), 0, nil) cBinTarget := fs.contentEnc.EncryptBlock([]byte(target), 0, nil)
cTarget = fs.nameTransform.B64.EncodeToString(cBinTarget) cTarget = fs.nameTransform.B64.EncodeToString(cBinTarget)
} }
// Handle long file name // Create ".name" file to store long file name (except in PlaintextNames mode)
cName := filepath.Base(cPath) cName := filepath.Base(cPath)
if !fs.args.PlaintextNames && nametransform.IsLongContent(cName) { if !fs.args.PlaintextNames && nametransform.IsLongContent(cName) {
var dirfd *os.File
dirfd, err = os.Open(filepath.Dir(cPath))
if err != nil {
return fuse.ToStatus(err)
}
defer dirfd.Close()
// Create ".name" file
err = fs.nameTransform.WriteLongName(dirfd, cName, linkName) err = fs.nameTransform.WriteLongName(dirfd, cName, linkName)
if err != nil { if err != nil {
return fuse.ToStatus(err) return fuse.ToStatus(err)
@ -454,16 +452,17 @@ func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (co
} }
} else { } else {
// Create symlink // Create symlink
err = os.Symlink(cTarget, cPath) err = syscallcompat.Symlinkat(cTarget, int(dirfd.Fd()), cName)
} }
if err != nil { if err != nil {
return fuse.ToStatus(err) return fuse.ToStatus(err)
} }
// Set owner // Set owner
if fs.args.PreserveOwner { if fs.args.PreserveOwner {
err = os.Lchown(cPath, int(context.Owner.Uid), int(context.Owner.Gid)) err = syscallcompat.Fchownat(int(dirfd.Fd()), cName, int(context.Owner.Uid),
int(context.Owner.Gid), unix.AT_SYMLINK_NOFOLLOW)
if err != nil { if err != nil {
tlog.Warn.Printf("Mknod: Lchown failed: %v", err) tlog.Warn.Printf("Symlink: Fchownat failed: %v", err)
} }
} }
return fuse.OK return fuse.OK