Re: [PATCH v2 2/2] virtiofs: allow skipping abort interface

[Vivek Goyal <vgoyal@redhat.com>]

On Wed, Jun 15, 2022 at 01:57:55PM +0800, Xie Yongji wrote:
> Virtio-fs does not support aborting requests which are being
> processed. Otherwise, it might trigger UAF since

What is full form of UAF? Use after free?

Thanks
Vivek

> virtio_fs_request_complete() doesn't know the requests are
> aborted. So let's remove the abort interface.
> 
> Fixes: 15c8e72e88e0 ("fuse: allow skipping control interface and forced unmount")
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---
>  fs/fuse/control.c   | 4 ++--
>  fs/fuse/fuse_i.h    | 4 ++++
>  fs/fuse/inode.c     | 1 +
>  fs/fuse/virtio_fs.c | 1 +
>  4 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/fuse/control.c b/fs/fuse/control.c
> index 7cede9a3bc96..d93d8ea3a090 100644
> --- a/fs/fuse/control.c
> +++ b/fs/fuse/control.c
> @@ -272,8 +272,8 @@ int fuse_ctl_add_conn(struct fuse_conn *fc)
>  
>  	if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
>  				 NULL, &fuse_ctl_waiting_ops) ||
> -	    !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
> -				 NULL, &fuse_ctl_abort_ops) ||
> +	    (!fc->no_abort_control && !fuse_ctl_add_dentry(parent, fc, "abort",
> +			S_IFREG | 0200, 1, NULL, &fuse_ctl_abort_ops)) ||
>  	    !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
>  				 1, NULL, &fuse_conn_max_background_ops) ||
>  	    !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index a47f14d0ee3f..e29a4e2f2b35 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -507,6 +507,7 @@ struct fuse_fs_context {
>  	bool default_permissions:1;
>  	bool allow_other:1;
>  	bool destroy:1;
> +	bool no_abort_control:1;
>  	bool no_force_umount:1;
>  	bool legacy_opts_show:1;
>  	enum fuse_dax_mode dax_mode;
> @@ -765,6 +766,9 @@ struct fuse_conn {
>  	/* Delete dentries that have gone stale */
>  	unsigned int delete_stale:1;
>  
> +	/** Do not create abort entry in fusectl fs */
> +	unsigned int no_abort_control:1;
> +
>  	/** Do not allow MNT_FORCE umount */
>  	unsigned int no_force_umount:1;
>  
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 4059c6898e08..02a16cd35f42 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1564,6 +1564,7 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
>  	fc->legacy_opts_show = ctx->legacy_opts_show;
>  	fc->max_read = max_t(unsigned int, 4096, ctx->max_read);
>  	fc->destroy = ctx->destroy;
> +	fc->no_abort_control = ctx->no_abort_control;
>  	fc->no_force_umount = ctx->no_force_umount;
>  
>  	err = -ENOMEM;
> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> index 24bcf4dbca2a..af369bea6dbb 100644
> --- a/fs/fuse/virtio_fs.c
> +++ b/fs/fuse/virtio_fs.c
> @@ -1287,6 +1287,7 @@ static inline void virtio_fs_ctx_set_defaults(struct fuse_fs_context *ctx)
>  	ctx->max_read = UINT_MAX;
>  	ctx->blksize = 512;
>  	ctx->destroy = true;
> +	ctx->no_abort_control = true;
>  	ctx->no_force_umount = true;
>  }
>  
> -- 
> 2.20.1
>