Re: [Qemu-devel] [V6 PATCH 7/9] virtio-9p: Support for creating special files

["Venkateswararao Jujjuri (JV)" <jvrao@linux.vnet.ibm.com>]

On 2/28/2011 3:22 AM, M. Mohan Kumar wrote:
> Add both chroot deamon and qemu side interfaces to create special files
> (directory, device nodes, links and symbolic links)
> 
> Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
> ---
>  hw/9pfs/virtio-9p-chroot-dm.c   |   57 ++++++++++++++++++++++++
>  hw/9pfs/virtio-9p-chroot-qemu.c |   19 ++++++++
>  hw/9pfs/virtio-9p-chroot.h      |    1 +
>  hw/9pfs/virtio-9p-local.c       |   93 ++++++++++++++++++++++++++-------------
>  4 files changed, 139 insertions(+), 31 deletions(-)
> 
> diff --git a/hw/9pfs/virtio-9p-chroot-dm.c b/hw/9pfs/virtio-9p-chroot-dm.c
> index 985d42b..0ead017 100644
> --- a/hw/9pfs/virtio-9p-chroot-dm.c
> +++ b/hw/9pfs/virtio-9p-chroot-dm.c
> @@ -119,6 +119,57 @@ unset_uid:
>      setfsuid(cur_uid);
>  }
> 
> +/*
> + * Create directory, symbolic link, link, device node and regular files
> + * Similar to create, but it does not return the fd of created object
> + * Returns 0 as file descriptor on success and -errno on failure in FdInfo
> + * structure
> + */
> +static void chroot_do_create_special(V9fsFileObjectRequest *request,
> +                FdInfo *fd_info)
> +{
> +    int cur_uid, cur_gid;
> +
> +    cur_uid = geteuid();
> +    cur_gid = getegid();
> +
> +    fd_info->fi_fd = -1;
> +    /* fd is not valid for create operations */
> +    fd_info->fi_flags = FI_FD_INVALID;
> +
> +    if (setfsuid(request->data.uid) < 0) {
> +        fd_info->fi_fd = -errno;
> +        return;
> +    }
> +    if (setfsgid(request->data.gid) < 0) {
> +        fd_info->fi_fd = -errno;
> +        goto unset_uid;
> +    }
> +
> +    switch (request->data.type) {
> +    case T_MKDIR:
> +        fd_info->fi_fd = mkdir(request->path.path, request->data.mode);
> +        break;
> +    case T_SYMLINK:
> +        fd_info->fi_fd = symlink(request->path.old_path, request->path.path);
> +        break;
> +    case T_LINK:
> +        fd_info->fi_fd = link(request->path.old_path, request->path.path);
> +        break;
> +    default:
> +        fd_info->fi_fd = mknod(request->path.path, request->data.mode,
> +                        request->data.dev);
> +        break;
> +    }
> +
> +    if (fd_info->fi_fd < 0) {
> +        fd_info->fi_fd = -errno;
> +    }
> +    setfsgid(cur_gid);
> +unset_uid:
> +    setfsuid(cur_uid);
> +}
> +
>  static int chroot_daemonize(int chroot_sock)
>  {
>      sigset_t sigset;
> @@ -216,6 +267,12 @@ int v9fs_chroot(FsContext *fs_ctx)
>          case T_CREATE:
>              chroot_do_create(&request, &fd_info);
>              break;
> +        case T_MKDIR:
> +        case T_SYMLINK:
> +        case T_LINK:
> +        case T_MKNOD:
> +            chroot_do_create_special(&request, &fd_info);
> +            break;
>          default:
>              fd_info.fi_flags = FI_FD_SOCKERR;
>              break;
> diff --git a/hw/9pfs/virtio-9p-chroot-qemu.c b/hw/9pfs/virtio-9p-chroot-qemu.c
> index 41f9db2..1a42dc2 100644
> --- a/hw/9pfs/virtio-9p-chroot-qemu.c
> +++ b/hw/9pfs/virtio-9p-chroot-qemu.c
> @@ -103,3 +103,22 @@ unlock:
>      qemu_mutex_unlock(&fs_ctx->chroot_mutex);
>      return fd;
>  }
> +
> +/* Return 0 on success or -errno on error */
> +int v9fs_create_special(FsContext *fs_ctx, V9fsFileObjectRequest *request)
> +{
> +    int fd, sock_error;
Since this is not fd; may be you can use some other variable like err or something?

> +    qemu_mutex_lock(&fs_ctx->chroot_mutex);
> +    if (fs_ctx->chroot_ioerror) {
> +        fd = -EIO;
> +        goto unlock;
> +    }
> +    v9fs_write_request(fs_ctx->chroot_socket, request);
> +        fd = v9fs_receivefd(fs_ctx->chroot_socket, &sock_error);
> +        if (fd < 0 && sock_error) {
> +            fs_ctx->chroot_ioerror = 1;
> +        }

Format??

- JV
> +unlock:
> +        qemu_mutex_unlock(&fs_ctx->chroot_mutex);
> +        return fd;
> +}
> diff --git a/hw/9pfs/virtio-9p-chroot.h b/hw/9pfs/virtio-9p-chroot.h
> index 4592807..f113ff1 100644
> --- a/hw/9pfs/virtio-9p-chroot.h
> +++ b/hw/9pfs/virtio-9p-chroot.h
> @@ -54,5 +54,6 @@ typedef struct V9fsFileObjectRequest
> 
>  int v9fs_chroot(FsContext *fs_ctx);
>  int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *or);
> +int v9fs_create_special(FsContext *fs_ctx, V9fsFileObjectRequest *request);
> 
>  #endif /* _QEMU_VIRTIO_9P_CHROOT_H */
> diff --git a/hw/9pfs/virtio-9p-local.c b/hw/9pfs/virtio-9p-local.c
> index 3fed16c..c92c5dd 100644
> --- a/hw/9pfs/virtio-9p-local.c
> +++ b/hw/9pfs/virtio-9p-local.c
> @@ -74,6 +74,28 @@ static int passthrough_create(FsContext *fs_ctx, const char *path, int flags,
>      return fd;
>  }
> 
> +static int passthrough_create_special(FsContext *fs_ctx, const char *oldpath,
> +                const char *path, FsCred *credp, int type)
> +{
> +    V9fsFileObjectRequest request;
> +    int retval;
> +
> +    retval = fill_fileobjectrequest(&request, path, credp);
> +    if (retval < 0) {
> +        return retval;
> +    }
> +    request.data.type = type;
> +    if (oldpath) {
> +        request.data.oldpath_len = strlen(oldpath);
> +        if (strlen(oldpath) > PATH_MAX) {
> +            return -ENAMETOOLONG;
> +        }
> +        strcpy(request.path.old_path, oldpath);
> +    }
> +    retval = v9fs_create_special(fs_ctx, &request);
> +    return retval;
> +}
> +
>  static int local_lstat(FsContext *fs_ctx, const char *path, struct stat *stbuf)
>  {
>      int err;
> @@ -291,8 +313,7 @@ static int local_mknod(FsContext *fs_ctx, const char *path, FsCred *credp)
>              serrno = errno;
>              goto err_end;
>          }
> -    } else if ((fs_ctx->fs_sm == SM_PASSTHROUGH) ||
> -               (fs_ctx->fs_sm == SM_NONE)) {
> +    } else if (fs_ctx->fs_sm == SM_NONE) {
>          err = mknod(rpath(fs_ctx, path), credp->fc_mode, credp->fc_rdev);
>          if (err == -1) {
>              return err;
> @@ -302,6 +323,12 @@ static int local_mknod(FsContext *fs_ctx, const char *path, FsCred *credp)
>              serrno = errno;
>              goto err_end;
>          }
> +    } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
> +        err = passthrough_create_special(fs_ctx, NULL, path, credp, T_MKNOD);
> +        if (err < 0) {
> +            serrno = errno;
> +            goto err_end;
> +        }
>      }
>      return err;
> 
> @@ -328,8 +355,7 @@ static int local_mkdir(FsContext *fs_ctx, const char *path, FsCred *credp)
>              serrno = errno;
>              goto err_end;
>          }
> -    } else if ((fs_ctx->fs_sm == SM_PASSTHROUGH) ||
> -               (fs_ctx->fs_sm == SM_NONE)) {
> +    } else if (fs_ctx->fs_sm == SM_NONE) {
>          err = mkdir(rpath(fs_ctx, path), credp->fc_mode);
>          if (err == -1) {
>              return err;
> @@ -339,6 +365,12 @@ static int local_mkdir(FsContext *fs_ctx, const char *path, FsCred *credp)
>              serrno = errno;
>              goto err_end;
>          }
> +    } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
> +        err = passthrough_create_special(fs_ctx, NULL, path, credp, T_MKDIR);
> +        if (err < 0) {
> +            serrno = errno;
> +            goto err_end;
> +        }
>      }
>      return err;
> 
> @@ -456,23 +488,19 @@ static int local_symlink(FsContext *fs_ctx, const char *oldpath,
>              serrno = errno;
>              goto err_end;
>          }
> -    } else if ((fs_ctx->fs_sm == SM_PASSTHROUGH) ||
> -               (fs_ctx->fs_sm == SM_NONE)) {
> +    } else if (fs_ctx->fs_sm == SM_NONE) {
>          err = symlink(oldpath, rpath(fs_ctx, newpath));
>          if (err) {
>              return err;
>          }
>          err = lchown(rpath(fs_ctx, newpath), credp->fc_uid, credp->fc_gid);
> -        if (err == -1) {
> -            /*
> -             * If we fail to change ownership and if we are
> -             * using security model none. Ignore the error
> -             */
> -            if (fs_ctx->fs_sm != SM_NONE) {
> -                serrno = errno;
> -                goto err_end;
> -            } else
> -                err = 0;
> +        err = 0;
> +    } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
> +        err = passthrough_create_special(fs_ctx, oldpath, newpath, credp,
> +                        T_SYMLINK);
> +        if (err < 0) {
> +            serrno = errno;
> +            goto err_end;
>          }
>      }
>      return err;
> @@ -483,24 +511,27 @@ err_end:
>      return err;
>  }
> 
> -static int local_link(FsContext *ctx, const char *oldpath, const char *newpath)
> +static int local_link(FsContext *fs_ctx, const char *oldpath,
> +                const char *newpath)
>  {
> -    char *tmp = qemu_strdup(rpath(ctx, oldpath));
>      int err, serrno = 0;
> 
> -    if (tmp == NULL) {
> -        return -ENOMEM;
> -    }
> -
> -    err = link(tmp, rpath(ctx, newpath));
> -    if (err == -1) {
> -        serrno = errno;
> -    }
> -
> -    qemu_free(tmp);
> -
> -    if (err == -1) {
> -        errno = serrno;
> +    if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
> +        err = passthrough_create_special(fs_ctx, oldpath, newpath, NULL,
> +                        T_LINK);
> +        if (err < 0) {
> +            serrno = errno;
> +        }
> +    } else {
> +        char *tmp = qemu_strdup(rpath(fs_ctx, oldpath));
> +        if (tmp == NULL) {
> +            return -ENOMEM;
> +        }
> +        err = link(tmp, rpath(fs_ctx, newpath));
> +        if (err == -1) {
> +            serrno = errno;
> +        }
> +        qemu_free(tmp);
>      }
> 
>      return err;