On Wed, Aug 10, 2022 at 12:10 PM Martin KaFai Lau <kafai@xxxxxx> wrote:
>
> Most of the code in bpf_setsockopt(SOL_SOCKET) are duplicated from
> the sk_setsockopt(). The number of supported optnames are
> increasing ever and so as the duplicated code.
>
> One issue in reusing sk_setsockopt() is that the bpf prog
> has already acquired the sk lock. This patch adds a
> has_current_bpf_ctx() to tell if the sk_setsockopt() is called from
> a bpf prog. The bpf prog calling bpf_setsockopt() is either running
> in_task() or in_serving_softirq(). Both cases have the current->bpf_ctx
> initialized. Thus, the has_current_bpf_ctx() only needs to
> test !!current->bpf_ctx.
>
> This patch also adds sockopt_{lock,release}_sock() helpers
> for sk_setsockopt() to use. These helpers will test
> has_current_bpf_ctx() before acquiring/releasing the lock. They are
> in EXPORT_SYMBOL for the ipv6 module to use in a latter patch.
>
> Note on the change in sock_setbindtodevice(). sockopt_lock_sock()
> is done in sock_setbindtodevice() instead of doing the lock_sock
> in sock_bindtoindex(..., lock_sk = true).
>
> Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
> ---
> include/linux/bpf.h | 14 ++++++++++++++
> include/net/sock.h | 3 +++
> net/core/sock.c | 30 +++++++++++++++++++++++++++---
> 3 files changed, 44 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index a627a02cf8ab..0a600b2013cc 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1966,6 +1966,16 @@ static inline bool unprivileged_ebpf_enabled(void)
> return !sysctl_unprivileged_bpf_disabled;
> }
>
> +/* Not all bpf prog type has the bpf_ctx.
> + * Only trampoline and cgroup-bpf have it.
this is not true already (perf_event and kprobe/uprobe/tp progs have
bpf_ctx as well) and can easily get out of sync in the future, so I'd
drop the list of types that support bpf_ctx.
> + * For the bpf prog type that has initialized the bpf_ctx,
> + * this function can be used to decide if a kernel function
> + * is called by a bpf program.
> + */
> +static inline bool has_current_bpf_ctx(void)
> +{
> + return !!current->bpf_ctx;
> +}
> #else /* !CONFIG_BPF_SYSCALL */
[...]
