Vladislav Efanov <VEfanov@xxxxxxxxx> writes:
> syzkaller got the following warning:
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 9992 at net/wireless/ibss.c:36 __cfg80211_ibss
>
> This warning is the result of the race condition between the following
> events:
>
> event1 event2 event3
> __ieee80211_sta_join_ibss() | |
> creates new cgf80211_bss | |
> structure. | |
> Calls cfg80211_ibss_joined() | |
> which will scheduled | |
> new event_work. | |
> ieee80211_ibss_disconnect() |
> is called due to connection |
> dropped/ibss leaves to |
> remove cfg80211_bss structure. |
> event_work starts.
> __cfg80211_ibss_joined()
> is called and WARNING is
> detected due to
> cfg80211_bss structure was
> removed by event2.
>
> It is a normal situation when connection is dropped during handshaking.
> So it looks reasonable to replace WARN_ON() with warning message to
> prevent false alarm.
>
> Found by Linux Verification Center (linuxtesting.org) with syzkaller.
> Fixes: 04a773ade068 ("cfg80211/nl80211: add IBSS API")
> Signed-off-by: Vladislav Efanov <VEfanov@xxxxxxxxx>
> ---
> net/wireless/ibss.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/wireless/ibss.c b/net/wireless/ibss.c
> index e6fdb0b8187d..93c8bee12bdf 100644
> --- a/net/wireless/ibss.c
> +++ b/net/wireless/ibss.c
> @@ -34,8 +34,10 @@ void __cfg80211_ibss_joined(struct net_device *dev, const u8 *bssid,
> bss = cfg80211_get_bss(wdev->wiphy, channel, bssid, NULL, 0,
> IEEE80211_BSS_TYPE_IBSS, IEEE80211_PRIVACY_ANY);
>
> - if (WARN_ON(!bss))
> + if (!bss) {
> + pr_warn("cfg80211: cfg80211_bss with bssid %s not found.\n", bssid);
> return;
> + }
If it's a normal case (disclaimer: didn't investigate that) the warning
message could be more descriptive. I suspect the user is just confused
after seeing that.
Also 'wifi:' missing from subject.
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