linux-kernel - [PATCH v2] wifi: brcmfmac: Replace 1-element arrays with flexible arrays

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Date:   Thu, 14 Sep 2023 09:02:27 +0200
From:   Juerg Haefliger <juerg.haefliger@...onical.com>
To:     juerg.haefliger@...onical.com
Cc:     SHA-cyfmac-dev-list@...ineon.com, aspriel@...il.com,
        brcm80211-dev-list.pdl@...adcom.com, franky.lin@...adcom.com,
        gustavoars@...nel.org, hante.meuleman@...adcom.com,
        hdegoede@...hat.com, keescook@...omium.org, kvalo@...nel.org,
        linus.walleij@...aro.org, linux-kernel@...r.kernel.org,
        linux-wireless@...r.kernel.org, marcan@...can.st,
        ryohei.kondo@...ress.com, stable@...r.kernel.org
Subject: [PATCH v2] wifi: brcmfmac: Replace 1-element arrays with flexible arrays

Since commit 2d47c6956ab3 ("ubsan: Tighten UBSAN_BOUNDS on GCC"),
UBSAN_BOUNDS no longer pretends 1-element arrays are unbounded. Walking
'element' and 'channel_list' will trigger warnings, so make them proper
flexible arrays.

False positive warnings were:

  UBSAN: array-index-out-of-bounds in drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:6984:20
  index 1 is out of range for type '__le32 [1]'

  UBSAN: array-index-out-of-bounds in drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:1126:27
  index 1 is out of range for type '__le16 [1]'

for these lines of code:

  6884  ch.chspec = (u16)le32_to_cpu(list->element[i]);

  1126  params_le->channel_list[i] = cpu_to_le16(chanspec);

Cc: stable@...r.kernel.org # 6.5+
Signed-off-by: Juerg Haefliger <juerg.haefliger@...onical.com>

---
v2:
  - Use element[] instead of DFA() in brcmf_chanspec_list.
  - Add Cc: stable tag
---
 .../wireless/broadcom/brcm80211/brcmfmac/fwil_types.h    | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h
index bece26741d3a..611d1a6aabb9 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h
@@ -442,7 +442,12 @@ struct brcmf_scan_params_v2_le {
 				 * fixed parameter portion is assumed, otherwise
 				 * ssid in the fixed portion is ignored
 				 */
-	__le16 channel_list[1];	/* list of chanspecs */
+	union {
+		__le16 padding;	/* Reserve space for at least 1 entry for abort
+				 * which uses an on stack brcmf_scan_params_v2_le
+				 */
+		DECLARE_FLEX_ARRAY(__le16, channel_list);	/* chanspecs */
+	};
 };
 
 struct brcmf_scan_results {
@@ -702,7 +707,7 @@ struct brcmf_sta_info_le {
 
 struct brcmf_chanspec_list {
 	__le32	count;		/* # of entries */
-	__le32	element[1];	/* variable length uint32 list */
+	__le32  element[];	/* variable length uint32 list */
 };
 
 /*
-- 
2.39.2