wifi: mac80211: fix memory leak in ieee80211_register_hw()

wifi: mac80211: fix memory leak in ieee80211_register_hw()

If kmemdup() fails while copying supported band structures, the error
path jumps to fail_rate. This skips rate_control_deinitialize() and
leaks the initialized local->rate_ctrl.

Fix this by adding a fail_band label that shares the rate-control cleanup
path before falling through to the remaining teardown.

The bug was first flagged by an experimental analysis tool we are
developing for kernel memory-management bugs while analyzing
v6.13-rc1. The tool is still under development and is not yet publicly
available. Manual inspection confirms that the bug is still present in
v7.1-rc7.

An x86_64 allyesconfig build showed no new warnings. As we do not have a
suitable mac80211 device/driver combination to test with, no runtime
testing was able to be performed.

Fixes: 09b4a4faf9d0 ("mac80211: introduce capability flags for VHT EXT NSS support")
Cc: stable@vger.kernel.org
Reviewed-by: Zilin Guan <zilin@seu.edu.cn>
Signed-off-by: Dawei Feng <dawei.feng@seu.edu.cn>
Link: https://patch.msgid.link/20260706143507.146131-1-dawei.feng@seu.edu.cn
Signed-off-by: Johannes Berg <johannes.berg@intel.com>