wifi: mac80211: fix use-after-free in chanctx code

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: fix use-after-free in chanctx code In ieee80211_vif_use_reserved_context(), when we have an old context and the new context's replace_state is set to IEEE80211_CHANCTX_REPLACE_NONE, we free the old context in ieee80211_vif_use_reserved_reassign(). Therefore, we cannot check the old_ctx anymore, so we should set it to NULL after this point. However, since the new_ctx replace state is clearly not IEEE80211_CHANCTX_REPLACES_OTHER, we're not going to do anything else in this function and can just return to avoid accessing the freed old_ctx.

References

• https://git.kernel.org/stable/c/88cc8f963febe192d6ded9df7217f92f380b449a
• https://git.kernel.org/stable/c/4ba81e794f0fad6234f644c2da1ae14d5b95e1c4
• https://git.kernel.org/stable/c/9f1e5cc85ad77e52f54049a94db0407445ae2a34
• https://git.kernel.org/stable/c/265bec4779a38b65e86a25120370f200822dfa76
• https://git.kernel.org/stable/c/6118bbdf69f4718b02d26bbcf2e497eb66004331
• https://git.kernel.org/stable/c/b79110f2bf6022e60e590d2e094728a8eec3e79e
• https://git.kernel.org/stable/c/82c8e7bbdd06c7ed58e22450cc5b37f33a25bb2c
• https://git.kernel.org/stable/c/4f05a9e15edcdf5b97e0d86ab6ecd5f187289f6c
• https://git.kernel.org/stable/c/2965c4cdf7ad9ce0796fac5e57debb9519ea721e