From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org, fsverity@lists.linux.dev, ast@kernel.org,
daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org,
kernel-team@meta.com, ebiggers@kernel.org, tytso@mit.edu,
roberto.sassu@huaweicloud.com
Subject: Re: [PATCH bpf-next 2/5] bpf, fsverity: Add kfunc bpf_get_fsverity_digest
Date: Tue, 17 Oct 2023 12:50:17 -0700 [thread overview]
Message-ID: <CAEf4BzbM0Ru4NpHNfn5Y=vQgfFAmeb+8Z+O6unuFkNr=9BrvKQ@mail.gmail.com> (raw)
In-Reply-To: <20231013182644.2346458-3-song@kernel.org>
On Fri, Oct 13, 2023 at 11:29 AM Song Liu <song@kernel.org> wrote:
>
> The kfunc can be used to read fsverity_digest, so that we can verify
> signature in BPF LSM.
>
> 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).
>
> Signed-off-by: Song Liu <song@kernel.org>
> ---
> fs/verity/measure.c | 66 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 66 insertions(+)
>
> diff --git a/fs/verity/measure.c b/fs/verity/measure.c
> index eec5956141da..2d4b2e6f5a5d 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>
>
> /**
> * fsverity_ioctl_measure() - get a verity file's digest
> @@ -100,3 +102,67 @@ int fsverity_get_digest(struct inode *inode,
> return hash_alg->digest_size;
> }
> EXPORT_SYMBOL_GPL(fsverity_get_digest);
> +
> +/* bpf kfuncs */
> +__diag_push();
> +__diag_ignore_all("-Wmissing-prototypes",
> + "kfuncs which will be used in BPF programs");
> +
> +/**
> + * bpf_get_fsverity_digest: read fsverity digest of file
> + * @file: file to get digest from
> + * @digest_ptr: (out) dynptr for struct fsverity_digest
> + *
> + * Read fsverity_digest of *file* into *digest_ptr*.
> + *
> + * Return: 0 on success, a negative value on error.
> + */
> +__bpf_kfunc int bpf_get_fsverity_digest(struct file *file, struct bpf_dynptr_kern *digest_ptr)
> +{
> + const struct inode *inode = file_inode(file);
> + struct fsverity_digest *arg = digest_ptr->data;
this can be null
I think we need some internal helpers that are similar to
bpf_dynptr_slice() that would handle invalid dynptr cases, as well as
abstract away potentially non-contiguous memory dynptr points to.
WDYT?
> + const struct fsverity_info *vi;
> + const struct fsverity_hash_alg *hash_alg;
> + int out_digest_sz;
> +
> + if (__bpf_dynptr_size(digest_ptr) < sizeof(struct fsverity_digest))
> + return -EINVAL;
> +
> + vi = fsverity_get_info(inode);
> + if (!vi)
> + return -ENODATA; /* not a verity file */
> +
> + hash_alg = vi->tree_params.hash_alg;
> +
> + arg->digest_algorithm = hash_alg - fsverity_hash_algs;
> + arg->digest_size = hash_alg->digest_size;
> +
> + out_digest_sz = __bpf_dynptr_size(digest_ptr) - sizeof(struct fsverity_digest);
> +
> + /* copy digest */
> + memcpy(arg->digest, vi->file_digest, min_t(int, hash_alg->digest_size, out_digest_sz));
> +
> + /* fill the extra buffer with zeros */
> + memset(arg->digest + arg->digest_size, 0, out_digest_sz - hash_alg->digest_size);
> +
> + return 0;
> +}
> +
> +__diag_pop();
> +
> +BTF_SET8_START(fsverity_set)
> +BTF_ID_FLAGS(func, bpf_get_fsverity_digest, KF_SLEEPABLE)
> +BTF_SET8_END(fsverity_set)
> +
> +const struct btf_kfunc_id_set bpf_fsverity_set = {
> + .owner = THIS_MODULE,
> + .set = &fsverity_set,
> +};
> +
> +static int __init bpf_fsverity_init(void)
> +{
> + return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,
> + &bpf_fsverity_set);
> +}
> +
> +late_initcall(bpf_fsverity_init);
> --
> 2.34.1
>
next prev parent reply other threads:[~2023-10-17 19:50 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20231013182644.2346458-1-song@kernel.org>
[not found] ` <20231013182644.2346458-3-song@kernel.org>
2023-10-15 7:07 ` [PATCH bpf-next 2/5] bpf, fsverity: Add kfunc bpf_get_fsverity_digest Eric Biggers
2023-10-16 20:10 ` Song Liu
2023-10-17 3:12 ` Eric Biggers
2023-10-17 5:35 ` Song Liu
2023-10-17 5:46 ` Eric Biggers
2023-10-17 14:16 ` Song Liu
2023-10-17 19:50 ` Andrii Nakryiko [this message]
[not found] ` <20231013182644.2346458-6-song@kernel.org>
2023-10-17 19:08 ` [PATCH bpf-next 5/5] selftests/bpf: Add test that use fsverity and xattr to sign a file Alexei Starovoitov
2023-10-17 20:36 ` Song Liu
[not found] ` <20231013182644.2346458-2-song@kernel.org>
2023-10-17 18:58 ` [PATCH bpf-next 1/5] bpf: Add kfunc bpf_get_file_xattr Andrii Nakryiko
2023-10-17 20:31 ` Song Liu
2023-10-17 21:52 ` Andrii Nakryiko
2023-10-17 22:16 ` Song Liu
2023-10-17 22:40 ` Andrii Nakryiko
2023-10-17 22:46 ` Song Liu
2023-10-18 1:42 ` Hou Tao
2023-10-17 19:10 ` Alexei Starovoitov
2023-11-02 1:19 ` KP Singh
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