dma-debug: fix a possible deadlock on radix_lock

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: dma-debug: fix a possible deadlock on radix_lock radix_lock() shouldn't be held while holding dma_hash_entry[idx].lock otherwise, there's a possible deadlock scenario when dma debug API is called holding rq_lock(): CPU0 CPU1 CPU2 dma_free_attrs() check_unmap() add_dma_entry() __schedule() //out (A) rq_lock() get_hash_bucket() (A) dma_entry_hash check_sync() (A) radix_lock() (W) dma_entry_hash dma_entry_free() (W) radix_lock() // CPU2's one (W) rq_lock() CPU1 situation can happen when it extending radix tree and it tries to wake up kswapd via wake_all_kswapd(). CPU2 situation can happen while perf_event_task_sched_out() (i.e. dma sync operation is called while deleting perf_event using etm and etr tmc which are Arm Coresight hwtracing driver backends). To remove this possible situation, call dma_entry_free() after put_hash_bucket() in check_unmap().

References

• https://git.kernel.org/stable/c/3ccce34a5c3f5c9541108a451657ade621524b32
• https://git.kernel.org/stable/c/efe1b9bbf356357fdff0399af361133d6e3ba18e
• https://git.kernel.org/stable/c/8c1b4fea8d62285f5e1a8194889b39661608bd8a
• https://git.kernel.org/stable/c/c212d91070beca0d03fef7bf988baf4ff4b3eee4
• https://git.kernel.org/stable/c/f2b95248a16c5186d1c658fc0aeb2f3bd95e5259
• https://git.kernel.org/stable/c/7543c3e3b9b88212fcd0aaf5cab5588797bdc7de