On Tue, Aug 20, 2024 at 3:18 AM Jordan Rome <linux@xxxxxxxxxxxxxx> wrote:
>
> This adds a kfunc wrapper around strncpy_from_user,
> which can be called from sleepable BPF programs.
>
> This matches the non-sleepable 'bpf_probe_read_user_str'
> helper except it includes an additional 'flags'
> param, which allows consumers to clear the entire
> destination buffer on success or failure.
>
> Signed-off-by: Jordan Rome <linux@xxxxxxxxxxxxxx>
> ---
> include/uapi/linux/bpf.h | 9 ++++++++
> kernel/bpf/helpers.c | 42 ++++++++++++++++++++++++++++++++++
> tools/include/uapi/linux/bpf.h | 9 ++++++++
> 3 files changed, 60 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index e05b39e39c3f..d3b69cb055c0 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -7513,4 +7513,13 @@ struct bpf_iter_num {
> __u64 __opaque[1];
> } __attribute__((aligned(8)));
>
> +/*
> + * Flags to control bpf_copy_from_user_str() behaviour.
> + * - BPF_F_PAD_ZEROS: Pad destination buffer with zeros. (See the respective
> + * helper documentation for details.)
> + */
> +enum {
> + BPF_F_PAD_ZEROS = (1ULL << 0)
Pls add , so this line doesn't have to be touched in the future.
> +++ b/tools/include/uapi/linux/bpf.h
> +enum {
> + BPF_F_PAD_ZEROS = (1ULL << 0)
and here, of course, as well.
> +__bpf_kfunc int bpf_copy_from_user_str(void *dst, u32 dst__szk, const void __user *unsafe_ptr__ign, u64 flags)
'k' in __szk is probably too restrictive.
It should work with __sz.
The difference is 'k' requires absolute constant
while __sz is ok with bounded value.
Probably worth adding a test as well.
