Re: [PATCH v5 bpf-next 5/9] bpf, fsverity: Add kfunc bpf_get_fsverity_digest

Eric Biggers
2023-10-24T23:03:39Z

On Mon, Oct 23, 2023 at 11:30:52PM -0700, Song Liu wrote:
> fsverity provides fast and reliable hash of files, namely fsverity_digest.
> The digest can be used by security solutions to verify file contents.
>
> Add new kfunc bpf_get_fsverity_digest() so that we can access fsverity from
> BPF LSM programs. This kfunc is added to fs/verity/measure.c because some
> data structure used in the function is private to fsverity
> (fs/verity/fsverity_private.h).
>
> To avoid recursion, bpf_get_fsverity_digest is only allowed in BPF LSM
> programs.
>
> Signed-off-by: Song Liu <song@kernel.org>
> ---
> fs/verity/fsverity_private.h | 10 +++++
> fs/verity/init.c | 1 +
> fs/verity/measure.c | 85 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 96 insertions(+)
>
> diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
> index d071a6e32581..f7124f89ab6f 100644
> --- a/fs/verity/fsverity_private.h
> +++ b/fs/verity/fsverity_private.h
> @@ -145,4 +145,14 @@ static inline void fsverity_init_signature(void)
>
> void __init fsverity_init_workqueue(void);
>
> +/* measure.c */
> +
> +#ifdef CONFIG_BPF_SYSCALL
> +int __init fsverity_init_bpf(void);
> +#else
> +static inline int fsverity_init_bpf(void)
> +{
> +}
> +#endif

This does not compile when !CONFIG_BPF_SYSCALL.

fsverity_init_bpf() probably shouldn't have a return value, given that this code
cannot be compiled as a loadable module. You can either panic on error, or
ignore the error. I don't think there are any other options.

Also, please keep the sections of this file in alphabetical order. The
measure.c section should go between init.c and open.c sections.

> diff --git a/fs/verity/measure.c b/fs/verity/measure.c
> index eec5956141da..4b0617ea0499 100644
> --- a/fs/verity/measure.c
> +++ b/fs/verity/measure.c
> @@ -8,6 +8,8 @@
> #include "fsverity_private.h"
>
> #include <linux/uaccess.h>
> +#include <linux/bpf.h>
> +#include <linux/btf.h>

Keep includes in alphabetical order, please.

- Eric