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

scsi: qla2xxx: Fix queue teardown NULL dma_free and bitmap locking

qla25xx_free_req_que() and qla25xx_free_rsp_que() have two pre-existing
bugs exposed on the error path of qla25xx_create_{req,rsp}_que():

 1. When dma_alloc_coherent() fails during queue creation, the error
    path calls the free function with req->ring / rsp->ring still NULL
    (from kzalloc).  The unconditional dma_free_coherent() with a NULL
    cpu_addr is undefined behavior and can panic.

 2. The free functions clear req_qid_map / rsp_qid_map under vport_lock,
    but the create functions protect the same bitmaps with mq_lock.
    This provides no mutual exclusion.  Additionally, the create error
    path clears the bit and releases mq_lock before calling the free
    function, creating a window where another thread can allocate the
    same que_id and have its ha->req_q_map entry clobbered by the
    subsequent lockless NULL assignment in the free function.

Fix by:

 - Guarding dma_free_coherent() with a NULL check on the ring pointer.

 - Using mq_lock (the lock held by all creators) in the free functions
   to atomically NULL the map entry and clear the bitmap bit.

 - Removing the now-redundant clear_bit blocks from the create error
   paths since the free functions handle it atomically.