wifi: mac80211: Don't finalize CSA in IBSS mode if state is disconnected

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: Don't finalize CSA in IBSS mode if state is disconnected 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().

References

• https://git.kernel.org/stable/c/cdb9a8da9b84800eb15506cd9363cf0cf059e677
• https://git.kernel.org/stable/c/1691a48aef0a82d1754b9853dae7e3f5cacdf70b
• https://git.kernel.org/stable/c/d9eb37db6a28b59a95a3461450ee209654c5f95b
• https://git.kernel.org/stable/c/66689c5c02acd4d76c28498fe220998610aec61e
• https://git.kernel.org/stable/c/dd649b49219a0388cc10fc40e4c2ea681566a780
• https://git.kernel.org/stable/c/552ba102a6898630a7d16887f29e606d6fabe508
• https://git.kernel.org/stable/c/864e280cb3a9a0f5212b16ef5057c4e692f7039d
• https://git.kernel.org/stable/c/15bc8966b6d3a5b9bfe4c9facfa02f2b69b1e5f0