On Sun, 14 Aug 2022 20:45:12 +0530 Siddh Raman Pant wrote:
> When we are not connected to a channel, sending channel "switch"
> announcement doesn't make any sense.
>
> The BSS list is empty in that case. This causes the for loop in
> cfg80211_get_bss() to be bypassed, so the function returns NULL
> (check line 1424 of net/wireless/scan.c), causing the WARN_ON()
> in ieee80211_ibss_csa_beacon() to get triggered (check line 500
> of net/mac80211/ibss.c), which was consequently reported on the
> syzkaller dashboard.
>
> Thus, check if we have an existing connection before generating
> the CSA beacon in ieee80211_ibss_finish_csa().
>
> Fixes: cd7760e62c2a ("mac80211: add support for CSA in IBSS mode")
> Bug report: https://syzkaller.appspot.com/bug?id=05603ef4ae8926761b678d2939a3b2ad28ab9ca6
> Reported-by: syzbot+b6c9fe29aefe68e4ad34@xxxxxxxxxxxxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
Tested-by: syzbot+b6c9fe29aefe68e4ad34@xxxxxxxxxxxxxxxxxxxxxxxxx
Syzbot is now booting properly and the test ran successfully.
Thanks,
Siddh
> Signed-off-by: Siddh Raman Pant <code@xxxxxxxx>
> ---
> The fixes commit is old, and syzkaller shows the problem exists for
> 4.19 and 4.14 as well, so CC'd stable list.
>
> net/mac80211/ibss.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
> index d56890e3fabb..9b283bbc7bb4 100644
> --- a/net/mac80211/ibss.c
> +++ b/net/mac80211/ibss.c
> @@ -530,6 +530,10 @@ int ieee80211_ibss_finish_csa(struct ieee80211_sub_if_data *sdata)
>
> sdata_assert_lock(sdata);
>
> + /* When not connected/joined, sending CSA doesn't make sense. */
> + if (ifibss->state != IEEE80211_IBSS_MLME_JOINED)
> + return -ENOLINK;
> +
> /* update cfg80211 bss information with the new channel */
> if (!is_zero_ether_addr(ifibss->bssid)) {
> cbss = cfg80211_get_bss(sdata->local->hw.wiphy,
> --
> 2.35.1
