[PATCH v2 1/2] fuse: Add a flag FUSE_SECURITY_CTX

[Casey Schaufler]

On 10/12/2021 11:06 AM, Vivek Goyal wrote:
> Add the FUSE_SECURITY_CTX flag for the `flags` field of the
> fuse_init_out struct.  When this flag is set the kernel will append the
> security context for a newly created inode to the request (create,
> mkdir, mknod, and symlink).  The server is responsible for ensuring that
> the inode appears atomically (preferrably) with the requested security context.
>
> For example, if the server is backed by a "real" linux file system then
> it can write the security context value to
> /proc/thread-self/attr/fscreate before making the syscall to create the
> inode.

his only works for SELinux, as I've mentioned before. Perhaps:

If the server is using SELinux and backed by a "real" linux file system
that supports extended attributes it can write the security context value
to /proc/thread-self/attr/fscreate before making the syscall to create
the inode.

>
> Vivek:
> This patch is slightly modified version of patch from
> Chirantan Ekbote <chirantan at chromium.org>. I made changes so that this
> patch applies to latest kernel.
>
> Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
> ---
>  include/uapi/linux/fuse.h | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> index 36ed092227fa..2fe54c80051a 100644
> --- a/include/uapi/linux/fuse.h
> +++ b/include/uapi/linux/fuse.h
> @@ -184,6 +184,10 @@
>   *
>   *  7.34
>   *  - add FUSE_SYNCFS
> + *
> + *  7.35
> + *  - add FUSE_SECURITY_CTX flag for fuse_init_out
> + *  - add security context to create, mkdir, symlink, and mknod requests
>   */
>  
>  #ifndef _LINUX_FUSE_H
> @@ -219,7 +223,7 @@
>  #define FUSE_KERNEL_VERSION 7
>  
>  /** Minor version number of this interface */
> -#define FUSE_KERNEL_MINOR_VERSION 34
> +#define FUSE_KERNEL_MINOR_VERSION 35
>  
>  /** The node ID of the root inode */
>  #define FUSE_ROOT_ID 1
> @@ -336,6 +340,8 @@ struct fuse_file_lock {
>   *			write/truncate sgid is killed only if file has group
>   *			execute permission. (Same as Linux VFS behavior).
>   * FUSE_SETXATTR_EXT:	Server supports extended struct fuse_setxattr_in
> + * FUSE_SECURITY_CTX:	add security context to create, mkdir, symlink, and
> + * 			mknod
>   */
>  #define FUSE_ASYNC_READ		(1 << 0)
>  #define FUSE_POSIX_LOCKS	(1 << 1)
> @@ -367,6 +373,7 @@ struct fuse_file_lock {
>  #define FUSE_SUBMOUNTS		(1 << 27)
>  #define FUSE_HANDLE_KILLPRIV_V2	(1 << 28)
>  #define FUSE_SETXATTR_EXT	(1 << 29)
> +#define FUSE_SECURITY_CTX	(1 << 30)
>  
>  /**
>   * CUSE INIT request/reply flags