netdev - Re: [PATCH v3 bpf-next 05/19] bpf: split read liveness into REG_LIVE_READ64 and REG_LIVE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190412180734.2f863fbe@cakuba.netronome.com>
Date:   Fri, 12 Apr 2019 18:07:34 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Jiong Wang <jiong.wang@...ronome.com>
Cc:     alexei.starovoitov@...il.com, daniel@...earbox.net,
        bpf@...r.kernel.org, netdev@...r.kernel.org,
        oss-drivers@...ronome.com
Subject: Re: [PATCH v3 bpf-next 05/19] bpf: split read liveness into
 REG_LIVE_READ64 and REG_LIVE_READ32

On Fri, 12 Apr 2019 22:59:38 +0100, Jiong Wang wrote:
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index c722015..3c5ca00 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -1135,7 +1135,7 @@ static int check_subprogs(struct bpf_verifier_env *env)
>   */
>  static int mark_reg_read(struct bpf_verifier_env *env,
>  			 const struct bpf_reg_state *state,
> -			 struct bpf_reg_state *parent)
> +			 struct bpf_reg_state *parent, u8 flags)
>  {
>  	bool writes = parent == state->parent; /* Observe write marks */
>  	int cnt = 0;
> @@ -1150,17 +1150,17 @@ static int mark_reg_read(struct bpf_verifier_env *env,
>  				parent->var_off.value, parent->off);
>  			return -EFAULT;
>  		}
> -		if (parent->live & REG_LIVE_READ)
> +		if ((parent->live & REG_LIVE_READ) == flags)
>  			/* The parentage chain never changes and
> -			 * this parent was already marked as LIVE_READ.
> +			 * this parent was already marked with all read bits.

No big deal, but I though said you'd modify this patch here...

>  			 * There is no need to keep walking the chain again and
> -			 * keep re-marking all parents as LIVE_READ.
> +			 * keep re-marking all parents with reads bits in flags.
>  			 * This case happens when the same register is read
>  			 * multiple times without writes into it in-between.
>  			 */
>  			break;
>  		/* ... then we depend on parent's value */
> -		parent->live |= REG_LIVE_READ;
> +		parent->live |= flags;
>  		state = parent;
>  		parent = state->parent;
>  		writes = true;

> @@ -6227,12 +6317,19 @@ static int propagate_liveness_reg(struct bpf_verifier_env *env,
>  				  struct bpf_reg_state *reg,
>  				  struct bpf_reg_state *parent_reg)
>  {
> +	u8 parent_bits = parent_reg->live & REG_LIVE_READ;
> +	u8 bits = reg->live & REG_LIVE_READ;
> +	u8 bits_diff = parent_bits ^ bits;
> +	u8 bits_prop = bits_diff & bits;
>  	int err;
>  
> -	if (parent_reg->live & REG_LIVE_READ || !(reg->live & REG_LIVE_READ))
> +	/* "reg" and "parent_reg" has the same read bits, or the bit doesn't
> +	 * belong to "reg".
> +	 */
> +	if (!bits_diff || !bits_prop)
>  		return 0;

.. and here?