RE: [PATCH 3/5] cifsd: add file operations

Namjae Jeon
2021-03-23T00:13:17Z

> On Mon, Mar 22, 2021 at 02:13:42PM +0900, Namjae Jeon wrote:
> > This adds file operations and buffer pool for cifsd.
>
> Some random notes:
>
> > +static void rollback_path_modification(char *filename) {
> > + if (filename) {
> > + filename--;
> > + *filename = '/';
> What an odd way to spell filename[-1] = '/';...
Okay. Will fix.
>
> > +int ksmbd_vfs_inode_permission(struct dentry *dentry, int acc_mode,
> > +bool delete) {
>
> > + if (delete) {
> > + struct dentry *parent;
> > +
> > + parent = dget_parent(dentry);
> > + if (!parent)
> > + return -EINVAL;
> > +
> > + if (inode_permission(&init_user_ns, d_inode(parent), MAY_EXEC | MAY_WRITE)) {
> > + dput(parent);
> > + return -EACCES;
> > + }
> > + dput(parent);
>
> Who's to guarantee that parent is stable? IOW, by the time of that
> inode_permission() call dentry might very well not be a child of that thing...
Okay, Will fix.
>
> > + parent = dget_parent(dentry);
> > + if (!parent)
> > + return 0;
> > +
> > + if (!inode_permission(&init_user_ns, d_inode(parent), MAY_EXEC | MAY_WRITE))
> > + *daccess |= FILE_DELETE_LE;
>
> Ditto.
Okay.
>
> > +int ksmbd_vfs_mkdir(struct ksmbd_work *work,
> > + const char *name,
> > + umode_t mode)
>
>
> > + err = vfs_mkdir(&init_user_ns, d_inode(path.dentry), dentry, mode);
> > + if (!err) {
> > + ksmbd_vfs_inherit_owner(work, d_inode(path.dentry),
> > + d_inode(dentry));
>
> ->mkdir() might very well return success, with dentry left unhashed negative.
> Look at the callers of vfs_mkdir() to see how it should be handled.
Okay, Will fix.
>
> > +static int check_lock_range(struct file *filp,
> > + loff_t start,
> > + loff_t end,
> > + unsigned char type)
> > +{
> > + struct file_lock *flock;
> > + struct file_lock_context *ctx = file_inode(filp)->i_flctx;
> > + int error = 0;
> > +
> > + if (!ctx || list_empty_careful(&ctx->flc_posix))
> > + return 0;
> > +
> > + spin_lock(&ctx->flc_lock);
> > + list_for_each_entry(flock, &ctx->flc_posix, fl_list) {
> > + /* check conflict locks */
> > + if (flock->fl_end >= start && end >= flock->fl_start) {
> > + if (flock->fl_type == F_RDLCK) {
> > + if (type == WRITE) {
> > + ksmbd_err("not allow write by shared lock\n");
> > + error = 1;
> > + goto out;
> > + }
> > + } else if (flock->fl_type == F_WRLCK) {
> > + /* check owner in lock */
> > + if (flock->fl_file != filp) {
> > + error = 1;
> > + ksmbd_err("not allow rw access by exclusive lock from other
> opens\n");
> > + goto out;
> > + }
> > + }
> > + }
> > + }
> > +out:
> > + spin_unlock(&ctx->flc_lock);
> > + return error;
> > +}
>
> WTF is that doing in smbd?
This code was added to pass the smb2 lock test of samba's smbtorture.
Will fix it.
>
> > + filp = fp->filp;
> > + inode = d_inode(filp->f_path.dentry);
>
> That should be file_inode(). Try it on overlayfs, watch it do interesting things...
Okay.
>
> > + nbytes = kernel_read(filp, rbuf, count, pos);
> > + if (nbytes < 0) {
> > + name = d_path(&filp->f_path, namebuf, sizeof(namebuf));
> > + if (IS_ERR(name))
> > + name = "(error)";
> > + ksmbd_err("smb read failed for (%s), err = %zd\n",
> > + name, nbytes);
>
> Do you really want the full pathname here? For (presumably) spew into syslog?
No, Will fix.
>
> > +int ksmbd_vfs_remove_file(struct ksmbd_work *work, char *name) {
> > + struct path parent;
> > + struct dentry *dir, *dentry;
> > + char *last;
> > + int err = -ENOENT;
> > +
> > + last = extract_last_component(name);
> > + if (!last)
> > + return -ENOENT;
>
> Yeccchhh...
I guess I change it err instead of -ENOENT.

>
> > + if (ksmbd_override_fsids(work))
> > + return -ENOMEM;
> > +
> > + err = kern_path(name, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &parent);
> > + if (err) {
> > + ksmbd_debug(VFS, "can't get %s, err %d\n", name, err);
> > + ksmbd_revert_fsids(work);
> > + rollback_path_modification(last);
> > + return err;
> > + }
> > +
> > + dir = parent.dentry;
> > + if (!d_inode(dir))
> > + goto out;
>
> Really? When does that happen?
Will fix.
>
> > +static int __ksmbd_vfs_rename(struct ksmbd_work *work,
> > + struct dentry *src_dent_parent,
> > + struct dentry *src_dent,
> > + struct dentry *dst_dent_parent,
> > + struct dentry *trap_dent,
> > + char *dst_name)
> > +{
> > + struct dentry *dst_dent;
> > + int err;
> > +
> > + spin_lock(&src_dent->d_lock);
> > + list_for_each_entry(dst_dent, &src_dent->d_subdirs, d_child) {
> > + struct ksmbd_file *child_fp;
> > +
> > + if (d_really_is_negative(dst_dent))
> > + continue;
> > +
> > + child_fp = ksmbd_lookup_fd_inode(d_inode(dst_dent));
> > + if (child_fp) {
> > + spin_unlock(&src_dent->d_lock);
> > + ksmbd_debug(VFS, "Forbid rename, sub file/dir is in use\n");
> > + return -EACCES;
> > + }
> > + }
> > + spin_unlock(&src_dent->d_lock);
>
> Hard NAK right there. That thing has no business poking at that level.
> And I'm pretty certain that it's racy as hell.
Okay. It was same reason(smbtorture test), will fix it also.

Thanks for your review!