netdev - Re: [PATCH bpf] bpf: disable and restore preemption in __BPF_PROG_RUN

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Date:   Mon, 23 Apr 2018 14:05:21 -0600
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Roman Gushchin <guro@...com>
Cc:     netdev@...r.kernel.org, kernel-team@...com,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf] bpf: disable and restore preemption in
 __BPF_PROG_RUN_ARRAY

On Mon, Apr 23, 2018 at 06:09:21PM +0100, Roman Gushchin wrote:
> Running bpf programs requires disabled preemption,
> however at least some* of the BPF_PROG_RUN_ARRAY users
> do not follow this rule.
> 
> To fix this bug, and also to make it not happen in the future,
> let's add explicit preemption disabling/re-enabling
> to the __BPF_PROG_RUN_ARRAY code.
> 
> * for example:
>  [   17.624472] RIP: 0010:__cgroup_bpf_run_filter_sk+0x1c4/0x1d0
>  ...
>  [   17.640890]  inet6_create+0x3eb/0x520
>  [   17.641405]  __sock_create+0x242/0x340
>  [   17.641939]  __sys_socket+0x57/0xe0
>  [   17.642370]  ? trace_hardirqs_off_thunk+0x1a/0x1c
>  [   17.642944]  SyS_socket+0xa/0x10
>  [   17.643357]  do_syscall_64+0x79/0x220
>  [   17.643879]  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> 
> Signed-off-by: Roman Gushchin <guro@...com>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Daniel Borkmann <daniel@...earbox.net>

Acked-by: Alexei Starovoitov <ast@...nel.org>