Re: [PATCH v3] wifi: mwifiex: Refactor 1-element array into flexible array in struct mwifiex_ie_types_chan_list_param_set

"Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx> · Wed, 7 Feb 2024 11:36:31 -0600

On 2/7/24 04:30, Kees Cook wrote:
struct mwifiex_ie_types_chan_list_param_set::chan_scan_param is treated
as a flexible array, so convert it into one so that it doesn't trip
the array bounds sanitizer[1]. Only a few places were using sizeof()
on the whole struct, so adjust those to follow the calculation pattern
to avoid including the trailing single element.

Examining binary output differences doesn't appear to show any literal
size values changing, though it is obfuscated a bit by the compiler
adjusting register usage and stack spill slots, etc.

Link: https://github.com/KSPP/linux/issues/51 [1]
Cc: Brian Norris <briannorris@xxxxxxxxxxxx>
Cc: Kalle Valo <kvalo@xxxxxxxxxx>
Cc: Dmitry Antipov <dmantipov@xxxxxxxxx>
Cc: Johannes Berg <johannes.berg@xxxxxxxxx>
Cc: zuoqilin <zuoqilin@xxxxxxxxxx>
Cc: Ruan Jinjie <ruanjinjie@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Cc: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Cc: linux-wireless@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

TLV and one-element arrays are always tricky to transform (into flex arrays),
but (unless I'm missing something that the maintainers might point out) this
looks good to me.

Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>

Thanks!
--
Gustavo

---
v3: catch two more cases of changed sizeof (gustavo)
v2: https://lore.kernel.org/linux-hardening/20240206183857.it.362-kees@xxxxxxxxxx/
v1: https://lore.kernel.org/linux-hardening/20240206163501.work.158-kees@xxxxxxxxxx/
---
  drivers/net/wireless/marvell/mwifiex/11n.c  | 12 +++++-------
  drivers/net/wireless/marvell/mwifiex/fw.h   |  2 +-
  drivers/net/wireless/marvell/mwifiex/scan.c | 14 ++++++--------
  3 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/11n.c b/drivers/net/wireless/marvell/mwifiex/11n.c
index 90e401100898..c0c635e74bc5 100644
--- a/drivers/net/wireless/marvell/mwifiex/11n.c
+++ b/drivers/net/wireless/marvell/mwifiex/11n.c
@@ -392,12 +392,10 @@ mwifiex_cmd_append_11n_tlv(struct mwifiex_private *priv,
  
  		chan_list =
  			(struct mwifiex_ie_types_chan_list_param_set *) *buffer;
-		memset(chan_list, 0,
-		       sizeof(struct mwifiex_ie_types_chan_list_param_set));
+		memset(chan_list, 0, struct_size(chan_list, chan_scan_param, 1));
  		chan_list->header.type = cpu_to_le16(TLV_TYPE_CHANLIST);
-		chan_list->header.len = cpu_to_le16(
-			sizeof(struct mwifiex_ie_types_chan_list_param_set) -
-			sizeof(struct mwifiex_ie_types_header));
+		chan_list->header.len =
+			cpu_to_le16(sizeof(struct mwifiex_chan_scan_param_set));
  		chan_list->chan_scan_param[0].chan_number =
  			bss_desc->bcn_ht_oper->primary_chan;
  		chan_list->chan_scan_param[0].radio_type =
@@ -411,8 +409,8 @@ mwifiex_cmd_append_11n_tlv(struct mwifiex_private *priv,
  					  (bss_desc->bcn_ht_oper->ht_param &
  					  IEEE80211_HT_PARAM_CHA_SEC_OFFSET));
  
-		*buffer += sizeof(struct mwifiex_ie_types_chan_list_param_set);
-		ret_len += sizeof(struct mwifiex_ie_types_chan_list_param_set);
+		*buffer += struct_size(chan_list, chan_scan_param, 1);
+		ret_len += struct_size(chan_list, chan_scan_param, 1);
  	}
  
  	if (bss_desc->bcn_bss_co_2040) {
diff --git a/drivers/net/wireless/marvell/mwifiex/fw.h b/drivers/net/wireless/marvell/mwifiex/fw.h
index 62f3c9a52a1d..3adc447b715f 100644
--- a/drivers/net/wireless/marvell/mwifiex/fw.h
+++ b/drivers/net/wireless/marvell/mwifiex/fw.h
@@ -770,7 +770,7 @@ struct mwifiex_chan_scan_param_set {
  
  struct mwifiex_ie_types_chan_list_param_set {
  	struct mwifiex_ie_types_header header;
-	struct mwifiex_chan_scan_param_set chan_scan_param[1];
+	struct mwifiex_chan_scan_param_set chan_scan_param[];
  } __packed;
  
  struct mwifiex_ie_types_rxba_sync {
diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c b/drivers/net/wireless/marvell/mwifiex/scan.c
index a2ddac363b10..0326b121747c 100644
--- a/drivers/net/wireless/marvell/mwifiex/scan.c
+++ b/drivers/net/wireless/marvell/mwifiex/scan.c
@@ -664,15 +664,14 @@ mwifiex_scan_channel_list(struct mwifiex_private *priv,
  
  			/* Copy the current channel TLV to the command being
  			   prepared */
-			memcpy(chan_tlv_out->chan_scan_param + tlv_idx,
+			memcpy(&chan_tlv_out->chan_scan_param[tlv_idx],
  			       tmp_chan_list,
-			       sizeof(chan_tlv_out->chan_scan_param));
+			       sizeof(*chan_tlv_out->chan_scan_param));
  
  			/* Increment the TLV header length by the size
  			   appended */
  			le16_unaligned_add_cpu(&chan_tlv_out->header.len,
-					       sizeof(
-						chan_tlv_out->chan_scan_param));
+					       sizeof(*chan_tlv_out->chan_scan_param));
  
  			/*
  			 * The tlv buffer length is set to the number of bytes
@@ -2369,12 +2368,11 @@ int mwifiex_cmd_802_11_bg_scan_config(struct mwifiex_private *priv,
  		     chan_idx < MWIFIEX_BG_SCAN_CHAN_MAX &&
  		     bgscan_cfg_in->chan_list[chan_idx].chan_number;
  		     chan_idx++) {
-			temp_chan = chan_list_tlv->chan_scan_param + chan_idx;
+			temp_chan = &chan_list_tlv->chan_scan_param[chan_idx];
  
  			/* Increment the TLV header length by size appended */
  			le16_unaligned_add_cpu(&chan_list_tlv->header.len,
-					       sizeof(
-					       chan_list_tlv->chan_scan_param));
+					       sizeof(*chan_list_tlv->chan_scan_param));
  
  			temp_chan->chan_number =
  				bgscan_cfg_in->chan_list[chan_idx].chan_number;
@@ -2413,7 +2411,7 @@ int mwifiex_cmd_802_11_bg_scan_config(struct mwifiex_private *priv,
  							   chan_scan_param);
  		le16_unaligned_add_cpu(&chan_list_tlv->header.len,
  				       chan_num *
-			     sizeof(chan_list_tlv->chan_scan_param[0]));
+			     sizeof(*chan_list_tlv->chan_scan_param));
  	}
  
  	tlv_pos += (sizeof(chan_list_tlv->header)







