On Tue, Jan 21, 2025 at 5:09 AM Juntong Deng <juntong.deng@xxxxxxxxxxx> wrote:
>
> Currently fs kfuncs are only available for LSM program type, but fs
> kfuncs are generic and useful for scenarios other than LSM.
>
> This patch makes fs kfuncs available for SYSCALL program type.
>
> Signed-off-by: Juntong Deng <juntong.deng@xxxxxxxxxxx>
> ---
> fs/bpf_fs_kfuncs.c | 14 ++++++--------
> .../selftests/bpf/progs/verifier_vfs_reject.c | 10 ----------
> 2 files changed, 6 insertions(+), 18 deletions(-)
>
> diff --git a/fs/bpf_fs_kfuncs.c b/fs/bpf_fs_kfuncs.c
> index 4a810046dcf3..8a7e9ed371de 100644
> --- a/fs/bpf_fs_kfuncs.c
> +++ b/fs/bpf_fs_kfuncs.c
> @@ -26,8 +26,6 @@ __bpf_kfunc_start_defs();
> * acquired by this BPF kfunc will result in the BPF program being rejected by
> * the BPF verifier.
> *
> - * This BPF kfunc may only be called from BPF LSM programs.
> - *
> * Internally, this BPF kfunc leans on get_task_exe_file(), such that calling
> * bpf_get_task_exe_file() would be analogous to calling get_task_exe_file()
> * directly in kernel context.
> @@ -49,8 +47,6 @@ __bpf_kfunc struct file *bpf_get_task_exe_file(struct task_struct *task)
> * passed to this BPF kfunc. Attempting to pass an unreferenced file pointer, or
> * any other arbitrary pointer for that matter, will result in the BPF program
> * being rejected by the BPF verifier.
> - *
> - * This BPF kfunc may only be called from BPF LSM programs.
> */
> __bpf_kfunc void bpf_put_file(struct file *file)
> {
> @@ -70,8 +66,6 @@ __bpf_kfunc void bpf_put_file(struct file *file)
> * reference, or else the BPF program will be outright rejected by the BPF
> * verifier.
> *
> - * This BPF kfunc may only be called from BPF LSM programs.
> - *
> * Return: A positive integer corresponding to the length of the resolved
> * pathname in *buf*, including the NUL termination character. On error, a
> * negative integer is returned.
> @@ -184,7 +178,8 @@ BTF_KFUNCS_END(bpf_fs_kfunc_set_ids)
> static int bpf_fs_kfuncs_filter(const struct bpf_prog *prog, u32 kfunc_id)
> {
> if (!btf_id_set8_contains(&bpf_fs_kfunc_set_ids, kfunc_id) ||
> - prog->type == BPF_PROG_TYPE_LSM)
> + prog->type == BPF_PROG_TYPE_LSM ||
> + prog->type == BPF_PROG_TYPE_SYSCALL)
> return 0;
> return -EACCES;
> }
> @@ -197,7 +192,10 @@ static const struct btf_kfunc_id_set bpf_fs_kfunc_set = {
>
> static int __init bpf_fs_kfuncs_init(void)
> {
> - return register_btf_kfunc_id_set(BPF_PROG_TYPE_LSM, &bpf_fs_kfunc_set);
> + int ret;
> +
> + ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_LSM, &bpf_fs_kfunc_set);
> + return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_fs_kfunc_set);
> }
>
> late_initcall(bpf_fs_kfuncs_init);
> diff --git a/tools/testing/selftests/bpf/progs/verifier_vfs_reject.c b/tools/testing/selftests/bpf/progs/verifier_vfs_reject.c
> index d6d3f4fcb24c..5aab75fd2fa5 100644
> --- a/tools/testing/selftests/bpf/progs/verifier_vfs_reject.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_vfs_reject.c
> @@ -148,14 +148,4 @@ int BPF_PROG(path_d_path_kfunc_invalid_buf_sz, struct file *file)
> return 0;
> }
>
> -SEC("fentry/vfs_open")
> -__failure __msg("calling kernel function bpf_path_d_path is not allowed")
> -int BPF_PROG(path_d_path_kfunc_non_lsm, struct path *path, struct file *f)
> -{
> - /* Calling bpf_path_d_path() from a non-LSM BPF program isn't permitted.
> - */
> - bpf_path_d_path(path, buf, sizeof(buf));
> - return 0;
> -}
A leftover from previous versions?
This test should still be rejected by the verifier.
