RE: [PATCH RESEND] wifi: iwlwifi: mvm: Fix __counted_by usage in cfg80211_wowlan_nd_*

[Korenblit, Miriam Rachel]

> -----Original Message-----
> From: Kees Cook <kees@xxxxxxxxxx>
> Sent: Monday, 16 December 2024 6:29
> To: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> Cc: Kees Cook <kees@xxxxxxxxxx>; Gustavo A . R . Silva <gustavoars@xxxxxxxxxx>;
> Korenblit, Miriam Rachel <miriam.rachel.korenblit@xxxxxxxxx>; Kalle Valo
> <kvalo@xxxxxxxxxx>; Berg, Johannes <johannes.berg@xxxxxxxxx>; Triebitz, Shaul
> <shaul.triebitz@xxxxxxxxx>; Grumbach, Emmanuel
> <emmanuel.grumbach@xxxxxxxxx>; Ben Shimol, Yedidya
> <yedidya.ben.shimol@xxxxxxxxx>; Berg, Benjamin <benjamin.berg@xxxxxxxxx>;
> Dmitry Antipov <dmantipov@xxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux-
> wireless@xxxxxxxxxxxxxxx; linux-hardening@xxxxxxxxxxxxxxx
> Subject: [PATCH RESEND] wifi: iwlwifi: mvm: Fix __counted_by usage in
> cfg80211_wowlan_nd_*
> 
> Both struct cfg80211_wowlan_nd_match and struct cfg80211_wowlan_nd_info
> pre-allocate space for channels and matches, but then may end up using fewer
> that the full allocation. Shrink the associated counter (n_channels and n_matches)
> after counting the results. This avoids compile-time (and run-time) warnings from
> __counted_by. (The counter member needs to be updated _before_ accessing the
> array index.)
> 
> Seen with coming GCC 15:
> 
> drivers/net/wireless/intel/iwlwifi/mvm/d3.c: In function
> 'iwl_mvm_query_set_freqs':
> drivers/net/wireless/intel/iwlwifi/mvm/d3.c:2877:66: warning: operation on
> 'match->n_channels' may be undefined [-Wsequence-point]
>  2877 |                                 match->channels[match->n_channels++] =
>       |                                                 ~~~~~~~~~~~~~~~~~^~
> drivers/net/wireless/intel/iwlwifi/mvm/d3.c:2885:66: warning: operation on
> 'match->n_channels' may be undefined [-Wsequence-point]
>  2885 |                                 match->channels[match->n_channels++] =
>       |                                                 ~~~~~~~~~~~~~~~~~^~
> drivers/net/wireless/intel/iwlwifi/mvm/d3.c: In function
> 'iwl_mvm_query_netdetect_reasons':
> drivers/net/wireless/intel/iwlwifi/mvm/d3.c:2982:58: warning: operation on
> 'net_detect->n_matches' may be undefined [-Wsequence-point]
>  2982 |                 net_detect->matches[net_detect->n_matches++] = match;
>       |                                     ~~~~~~~~~~~~~~~~~~~~~^~
> 
> Fixes: aa4ec06c455d ("wifi: cfg80211: use __counted_by where appropriate")
> Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20240619211233.work.355-kees@xxxxxxxxxx
> Signed-off-by: Kees Cook <kees@xxxxxxxxxx>
> ---
> Pinging this patch again, see
> https://lore.kernel.org/lkml/20240619211233.work.355-kees@xxxxxxxxxx/
> ---
>  drivers/net/wireless/intel/iwlwifi/mvm/d3.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
> b/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
> index f85c01e04ebf..7d973546c9fb 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
> +++ b/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
> @@ -2954,6 +2954,7 @@ static void iwl_mvm_query_set_freqs(struct iwl_mvm
> *mvm,
>  				    int idx)
>  {
>  	int i;
> +	int n_channels = 0;
> 
>  	if (fw_has_api(&mvm->fw->ucode_capa,
>  		       IWL_UCODE_TLV_API_SCAN_OFFLOAD_CHANS)) { @@ -
> 2962,7 +2963,7 @@ static void iwl_mvm_query_set_freqs(struct iwl_mvm
> *mvm,
> 
>  		for (i = 0; i < SCAN_OFFLOAD_MATCHING_CHANNELS_LEN * 8;
> i++)
>  			if (matches[idx].matching_channels[i / 8] & (BIT(i % 8)))
> -				match->channels[match->n_channels++] =
> +				match->channels[n_channels++] =
>  					mvm->nd_channels[i]->center_freq;
>  	} else {
>  		struct iwl_scan_offload_profile_match_v1 *matches = @@ -
> 2970,9 +2971,11 @@ static void iwl_mvm_query_set_freqs(struct iwl_mvm
> *mvm,
> 
>  		for (i = 0; i < SCAN_OFFLOAD_MATCHING_CHANNELS_LEN_V1 *
> 8; i++)
>  			if (matches[idx].matching_channels[i / 8] & (BIT(i % 8)))
> -				match->channels[match->n_channels++] =
> +				match->channels[n_channels++] =
>  					mvm->nd_channels[i]->center_freq;
>  	}
> +	/* We may have ended up with fewer channels than we allocated. */
> +	match->n_channels = n_channels;
>  }
> 
>  /**
> @@ -3053,6 +3056,8 @@ static void iwl_mvm_query_netdetect_reasons(struct
> iwl_mvm *mvm,
>  			     GFP_KERNEL);
>  	if (!net_detect || !n_matches)
>  		goto out_report_nd;
> +	net_detect->n_matches = n_matches;
> +	n_matches = 0;
> 
>  	for_each_set_bit(i, &matched_profiles, mvm->n_nd_match_sets) {
>  		struct cfg80211_wowlan_nd_match *match; @@ -3066,8
> +3071,9 @@ static void iwl_mvm_query_netdetect_reasons(struct iwl_mvm
> *mvm,
>  				GFP_KERNEL);
>  		if (!match)
>  			goto out_report_nd;
> +		match->n_channels = n_channels;
> 
> -		net_detect->matches[net_detect->n_matches++] = match;
> +		net_detect->matches[n_matches++] = match;
> 
>  		/* We inverted the order of the SSIDs in the scan
>  		 * request, so invert the index here.
> @@ -3082,6 +3088,8 @@ static void iwl_mvm_query_netdetect_reasons(struct
> iwl_mvm *mvm,
> 
>  		iwl_mvm_query_set_freqs(mvm, d3_data->nd_results, match, i);
>  	}
> +	/* We may have fewer matches than we allocated. */
> +	net_detect->n_matches = n_matches;
> 
>  out_report_nd:
>  	wakeup.net_detect = net_detect;
> --
> 2.34.1

Hi ,

The patch was already applied and marked in Patchwork as such. 

Miri