netdev - Re: [PATCH bpf 1/2] bpf: fix panic in prog load calls cleanup

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Date:   Fri, 15 Jun 2018 08:56:24 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Daniel Borkmann <daniel@...earbox.net>
CC:     <ast@...nel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf 1/2] bpf: fix panic in prog load calls cleanup

On Fri, Jun 15, 2018 at 02:30:47AM +0200, Daniel Borkmann wrote:
> While testing I found that when hitting error path in bpf_prog_load()
> where we jump to free_used_maps and prog contained BPF to BPF calls
> that were JITed earlier, then we never clean up the bpf_prog_kallsyms_add()
> done under jit_subprogs(). Add proper API to make BPF kallsyms deletion
> more clear and fix that.
> 
> Fixes: 1c2a088a6626 ("bpf: x64: add JIT support for multi-function programs")
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Martin KaFai Lau <kafai@...com>

> ---
>  include/linux/filter.h |  3 +++
>  kernel/bpf/core.c      | 14 ++++++++++++++
>  kernel/bpf/syscall.c   |  8 ++------
>  3 files changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 45fc0f5..297c56f 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -961,6 +961,9 @@ static inline void bpf_prog_kallsyms_del(struct bpf_prog *fp)
>  }
>  #endif /* CONFIG_BPF_JIT */
>  
> +void bpf_prog_kallsyms_del_subprogs(struct bpf_prog *fp);
> +void bpf_prog_kallsyms_del_all(struct bpf_prog *fp);
> +
>  #define BPF_ANC		BIT(15)
>  
>  static inline bool bpf_needs_clear_a(const struct sock_filter *first)
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 9f14937..1061968 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -350,6 +350,20 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
>  	return prog_adj;
>  }
>  
> +void bpf_prog_kallsyms_del_subprogs(struct bpf_prog *fp)
> +{
> +	int i;
> +
> +	for (i = 0; i < fp->aux->func_cnt; i++)
> +		bpf_prog_kallsyms_del(fp->aux->func[i]);
> +}
> +
> +void bpf_prog_kallsyms_del_all(struct bpf_prog *fp)
> +{
> +	bpf_prog_kallsyms_del_subprogs(fp);
> +	bpf_prog_kallsyms_del(fp);
> +}
> +
>  #ifdef CONFIG_BPF_JIT
>  /* All BPF JIT sysctl knobs here. */
>  int bpf_jit_enable   __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_ALWAYS_ON);
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 0fa2062..0f62692 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -1034,14 +1034,9 @@ static void __bpf_prog_put_rcu(struct rcu_head *rcu)
>  static void __bpf_prog_put(struct bpf_prog *prog, bool do_idr_lock)
>  {
>  	if (atomic_dec_and_test(&prog->aux->refcnt)) {
> -		int i;
> -
>  		/* bpf_prog_free_id() must be called first */
>  		bpf_prog_free_id(prog, do_idr_lock);
> -
> -		for (i = 0; i < prog->aux->func_cnt; i++)
> -			bpf_prog_kallsyms_del(prog->aux->func[i]);
> -		bpf_prog_kallsyms_del(prog);
> +		bpf_prog_kallsyms_del_all(prog);
>  
>  		call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu);
>  	}
> @@ -1384,6 +1379,7 @@ static int bpf_prog_load(union bpf_attr *attr)
>  	return err;
>  
>  free_used_maps:
> +	bpf_prog_kallsyms_del_subprogs(prog);
>  	free_used_maps(prog->aux);
>  free_prog:
>  	bpf_prog_uncharge_memlock(prog);
> -- 
> 2.9.5
>