Since adding __counted_by(n_channels) to struct cfg80211_scan_request,
anything adding to the channels array must increment n_channels first.
Move n_channels increment earlier.

Reported-by: John Rowley <lkml@johnrowley.me>
Closes: https://lore.kernel.org/stable/1815535c709ba9d9.156c6a5c9cdf6e59.b249b6b6a5ee4634@localhost.localdomain/
Fixes: aa4ec06c455d ("wifi: cfg80211: use __counted_by where appropriate")
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Dmitry Antipov <dmantipov@yandex.ru>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: linux-wireless@vger.kernel.org
---
 net/wireless/scan.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 1c6fd45aa809..ccdbeb604639 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -763,12 +763,11 @@ static  void cfg80211_scan_req_add_chan(struct cfg80211_scan_request *request,
 		}
 	}
 
+	request->n_channels++;
 	request->channels[n_channels] = chan;
 	if (add_to_6ghz)
 		request->scan_6ghz_params[request->n_6ghz_params].channel_idx =
 			n_channels;
-
-	request->n_channels++;
 }
 
 static bool cfg80211_find_ssid_match(struct cfg80211_colocated_ap *ap,
-- 
2.34.1

On 30/12/24 12:36, Kees Cook wrote:
> Since adding __counted_by(n_channels) to struct cfg80211_scan_request,
> anything adding to the channels array must increment n_channels first.
> Move n_channels increment earlier.
> 
> Reported-by: John Rowley <lkml@johnrowley.me>
> Closes: https://lore.kernel.org/stable/1815535c709ba9d9.156c6a5c9cdf6e59.b249b6b6a5ee4634@localhost.localdomain/
> Fixes: aa4ec06c455d ("wifi: cfg80211: use __counted_by where appropriate")
> Signed-off-by: Kees Cook <kees@kernel.org>

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

-Gustavo

> ---
> Cc: Johannes Berg <johannes@sipsolutions.net>
> Cc: Dmitry Antipov <dmantipov@yandex.ru>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: linux-wireless@vger.kernel.org
> ---
>   net/wireless/scan.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/wireless/scan.c b/net/wireless/scan.c
> index 1c6fd45aa809..ccdbeb604639 100644
> --- a/net/wireless/scan.c
> +++ b/net/wireless/scan.c
> @@ -763,12 +763,11 @@ static  void cfg80211_scan_req_add_chan(struct cfg80211_scan_request *request,
>   		}
>   	}
>   
> +	request->n_channels++;
>   	request->channels[n_channels] = chan;
>   	if (add_to_6ghz)
>   		request->scan_6ghz_params[request->n_6ghz_params].channel_idx =
>   			n_channels;
> -
> -	request->n_channels++;
>   }
>   
>   static bool cfg80211_find_ssid_match(struct cfg80211_colocated_ap *ap,