wifi: wlcore: Return -ENOMEM instead of -EAGAIN if there is not enough headroom

In the Linux kernel, the following vulnerability has been resolved:

wifi: wlcore: Return -ENOMEM instead of -EAGAIN if there is not enough headroom

Since upstream commit e75665dd0968 ("wifi: wlcore: ensure skb headroom

before skb_push"), wl1271_tx_allocate() and with it

wl1271_prepare_tx_frame() returns -EAGAIN if pskb_expand_head() fails.

However, in wlcore_tx_work_locked(), a return value of -EAGAIN from

wl1271_prepare_tx_frame() is interpreted as the aggregation buffer being

full. This causes the code to flush the buffer, put the skb back at the

head of the queue, and immediately retry the same skb in a tight while

loop.

Because wlcore_tx_work_locked() holds wl->mutex, and the retry happens

immediately with GFP_ATOMIC, this will result in an infinite loop and a

CPU soft lockup. Return -ENOMEM instead so the packet is dropped and

the loop terminates.

The problem was found by an experimental code review agent based on

gemini-3.1-pro while reviewing backports into v6.18.y.