Le 19/06/2024 à 23:12, Kees Cook a écrit :
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")
Signed-off-by: Kees Cook <kees-DgEjT+Ai2ygdnm+yROfE0A@xxxxxxxxxxxxxxxx>
---
Cc: Miri Korenblit <miriam.rachel.korenblit-ral2JQCrhuEAvxtiuMwx3w@xxxxxxxxxxxxxxxx>
Cc: Kalle Valo <kvalo-DgEjT+Ai2ygdnm+yROfE0A@xxxxxxxxxxxxxxxx>
Cc: Johannes Berg <johannes.berg-ral2JQCrhuEAvxtiuMwx3w@xxxxxxxxxxxxxxxx>
Cc: Gustavo A. R. Silva <gustavoars-DgEjT+Ai2ygdnm+yROfE0A@xxxxxxxxxxxxxxxx>
Cc: Luca Coelho <luciano.coelho-ral2JQCrhuEAvxtiuMwx3w@xxxxxxxxxxxxxxxx>
Cc: Gregory Greenman <gregory.greenman-ral2JQCrhuEAvxtiuMwx3w@xxxxxxxxxxxxxxxx>
Cc: Yedidya Benshimol <yedidya.ben.shimol-ral2JQCrhuEAvxtiuMwx3w@xxxxxxxxxxxxxxxx>
Cc: Haim Dreyfuss <haim.dreyfuss-ral2JQCrhuEAvxtiuMwx3w@xxxxxxxxxxxxxxxx>
Cc: linux-wireless-u79uwXL29TY76Z2rM5mHXA@xxxxxxxxxxxxxxxx
---
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 54f4acbbd05b..9cd03ea4680d 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
@@ -2866,6 +2866,7 @@ 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)) {
@@ -2874,7 +2875,7 @@ 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 =
@@ -2882,9 +2883,11 @@ 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;
Hi,
I'm sorry but I don't understand the patch.
You state that "The counter member needs to be updated _before_
accessing the array index.". I agree with it.
But this patch seems to steel update it *after*.
My understanding is that 'match', is allocated by :
match = kzalloc(struct_size(match, channels, n_channels), GFP_KERNEL);
So match->n_channels is *0* when iwl_mvm_query_set_freqs() is called.
So the __counted_by() mechanism should complain when doing
match->channels[n_channels++] = mvm->nd_channels[i]->center_freq;
whatever n_channels value is.
I would expect the solution to be related to pre-increment instead of
post-increment. Something like:
> - match->channels[match->n_channels++] =
> + match->channels[++match->n_channels] =
> mvm->nd_channels[i]->center_freq;
Did I miss something obvious or I don't understand how __counted_by() works?
CJ
}
/**
@@ -2965,6 +2968,8 @@ 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;
@@ -2978,8 +2983,9 @@ 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.
@@ -2994,6 +3000,8 @@ 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;
