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Re: [PATCH] wifi: brcmfmac: Replace 1-element arrays with flexible arrays

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On 9/13/23 00:54, Juerg Haefliger wrote:
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);

Signed-off-by: Juerg Haefliger <juerg.haefliger@xxxxxxxxxxxxx>
---
  .../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..ed723a5b5d54 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 */
+	DECLARE_FLEX_ARRAY(__le32, element);	/* variable length uint32 list */

If no padding is needed, as in the other case, then DFA() is not necessary.
Just remove the 1 from the array declaration:

 struct brcmf_chanspec_list {
        __le32  count;          /* # of entries */
-       __le32  element[1];     /* variable length uint32 list */
+       __le32  element[];      /* variable length uint32 list */
 };

--
Gustavo

  };
/*



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