Subject: Re: [PATCH ipsec-next v10 2/3] xfrm: Add dir validation to "out" data path lookup

From: Simon Horman <[email-masked]>
Date: Thu, 18 Apr 2024 10:24:21 +0100

On Thu, Apr 11, 2024 at 11:42:13AM +0200, Antony Antony wrote:
> Introduces validation for the x->dir attribute within the XFRM output
> data lookup path. If the configured direction does not match the expected
> direction, out, increment the XfrmOutDirError counter and drop the packet
> to ensure data integrity and correct flow handling.
> 
> grep -vw 0 /proc/net/xfrm_stat
> XfrmOutPolError         	2
> XfrmOutDirError         	2
> 
> Signed-off-by: Antony Antony <[email-masked]>

...

> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> index 6affe5cd85d8..7deeb21dae15 100644
> --- a/net/xfrm/xfrm_policy.c
> +++ b/net/xfrm/xfrm_policy.c
> @@ -2489,6 +2489,12 @@ xfrm_tmpl_resolve_one(struct xfrm_policy *policy, const struct flowi *fl,
>  
>  		x = xfrm_state_find(remote, local, fl, tmpl, policy, &error,
>  				    family, policy->if_id);
> +		if (x->dir && x->dir != XFRM_SA_DIR_OUT) {
> +			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTDIRERROR);
> +			xfrm_state_put(x);
> +			error = -EINVAL;
> +			goto fail;
> +		}

Hi Antony,

the line below assumes that x may be NULL,
but the new code above dereferences x unconditionally.
Is this ok?

Flagged by Smatch.

>  
>  		if (x && x->km.state == XFRM_STATE_VALID) {
>  			xfrm[nx++] = x;

...