Re: [PATCH] BPF: Disable on PREEMPT_RT

[Daniel Borkmann <daniel@iogearbox.net>]

On Thu, Oct 17, 2019 at 11:05:01AM +0200, Sebastian Andrzej Siewior wrote:
> Disable BPF on PREEMPT_RT because
> - it allocates and frees memory in atomic context
> - it uses up_read_non_owner()
> - BPF_PROG_RUN() expects to be invoked in non-preemptible context

For the latter you'd also need to disable seccomp-BPF and everything
cBPF related as they are /all/ invoked via BPF_PROG_RUN() ...

> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> 
> I tried to fix the memory allocations in 
>   http://lkml.kernel.org/r/20190410143025.11997-1-bigeasy@linutronix.de
> 
> but I have no idea how to address the other two issues.
> 
>  init/Kconfig    |    1 +
>  net/kcm/Kconfig |    1 +
>  2 files changed, 2 insertions(+)
> 
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1629,6 +1629,7 @@ config KALLSYMS_BASE_RELATIVE
>  # syscall, maps, verifier
>  config BPF_SYSCALL
>  	bool "Enable bpf() system call"
> +	depends on !PREEMPT_RT
>  	select BPF
>  	select IRQ_WORK
>  	default n
> --- a/net/kcm/Kconfig
> +++ b/net/kcm/Kconfig
> @@ -3,6 +3,7 @@
>  config AF_KCM
>  	tristate "KCM sockets"
>  	depends on INET
> +	depends on !PREEMPT_RT
>  	select BPF_SYSCALL
>  	select STREAM_PARSER
>  	---help---