In the Linux kernel, the following vulnerability has been resolved:
scsi: qla2xxx: Avoid req_q_map double-read in qla2x00_error_entry()
qla2x00_error_entry() reads ha->req_q_map[que] twice: once for the NULL
check and again when assigning it to req. The map slot is cleared by
qla25xx_free_req_que() (ha->req_q_map[que_id] = NULL under mq_lock)
during queue teardown, while the response-queue interrupt that drives
qla2x00_error_entry() is still registered (the IRQ is released later in
qla25xx_free_rsp_que()). If the slot is set to NULL between the two
reads, req becomes NULL and is dereferenced.
Read the slot once into req and NULL-check the local before use. mq_lock
is a mutex and cannot be taken from interrupt context, so the single
read plus local check is the appropriate fix for the reported NULL
dereference.
