CVE-2021-46964

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

scsi: qla2xxx: Reserve extra IRQ vectors

Commit a6dcfe08487e ("scsi: qla2xxx: Limit interrupt vectors to number of CPUs") lowers the number of allocated MSI-X vectors to the number of CPUs.

That breaks vector allocation assumptions in qla83xx_iospace_config(), qla24xx_enable_msix() and qla2x00_iospace_config(). Either of the functions computes maximum number of qpairs as:

ha->max_qpairs = ha->msix_count - 1 (MB interrupt) - 1 (default response queue) - 1 (ATIO, in dual or pure target mode)

max_qpairs is set to zero in case of two CPUs and initiator mode. The number is then used to allocate ha->queue_pair_map inside qla2x00_alloc_queues(). No allocation happens and ha->queue_pair_map is left NULL but the driver thinks there are queue pairs available.

qla2xxx_queuecommand() tries to find a qpair in the map and crashes:

if (ha->mqenable) { uint32_t tag; uint16_t hwq; struct qla_qpair *qpair = NULL;

      tag = blk_mq_unique_tag(cmd->request);
      hwq = blk_mq_unique_tag_to_hwq(tag);
      qpair = ha->queue_pair_map[hwq]; # <- HERE

      if (qpair)
              return qla2xxx_mqueuecommand(host, cmd, qpair);

}

BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 0 PID: 72 Comm: kworker/u4:3 Tainted: G W 5.10.0-rc1+ #25 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014 Workqueue: scsi_wq_7 fc_scsi_scan_rport [scsi_transport_fc] RIP: 0010:qla2xxx_queuecommand+0x16b/0x3f0 [qla2xxx] Call Trace: scsi_queue_rq+0x58c/0xa60 blk_mq_dispatch_rq_list+0x2b7/0x6f0 ? __sbitmap_get_word+0x2a/0x80 __blk_mq_sched_dispatch_requests+0xb8/0x170 blk_mq_sched_dispatch_requests+0x2b/0x50...