CVE-2022-49901

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

blk-mq: Fix kmemleak in blk_mq_init_allocated_queue

There is a kmemleak caused by modprobe null_blk.ko

unreferenced object 0xffff8881acb1f000 (size 1024):
  comm "modprobe", pid 836, jiffies 4294971190 (age 27.068s)
  hex dump (first 32 bytes):
    00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00  .....N..........
    ff ff ff ff ff ff ff ff 00 53 99 9e ff ff ff ff  .........S......
  backtrace:
    [<000000004a10c249>] kmalloc_node_trace+0x22/0x60
    [<00000000648f7950>] blk_mq_alloc_and_init_hctx+0x289/0x350
    [<00000000af06de0e>] blk_mq_realloc_hw_ctxs+0x2fe/0x3d0
    [<00000000e00c1872>] blk_mq_init_allocated_queue+0x48c/0x1440
    [<00000000d16b4e68>] __blk_mq_alloc_disk+0xc8/0x1c0
    [<00000000d10c98c3>] 0xffffffffc450d69d
    [<00000000b9299f48>] 0xffffffffc4538392
    [<0000000061c39ed6>] do_one_initcall+0xd0/0x4f0
    [<00000000b389383b>] do_init_module+0x1a4/0x680
    [<0000000087cf3542>] load_module+0x6249/0x7110
    [<00000000beba61b8>] __do_sys_finit_module+0x140/0x200
    [<00000000fdcfff51>] do_syscall_64+0x35/0x80
    [<000000003c0f1f71>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

That is because q->ma_ops is set to NULL before blk_release_queue is
called.

blk_mq_init_queue_data
  blk_mq_init_allocated_queue
    blk_mq_realloc_hw_ctxs
      for (i = 0; i < set->nr_hw_queues; i++) {
        old_hctx = xa_load(&q->hctx_table, i);
        if (!blk_mq_alloc_and_init_hctx(.., i, ..))		[1]
          if (!old_hctx)
	    break;

      xa_for_each_start(&q->hctx_table, j, hctx, j)
        blk_mq_exit_hctx(q, set, hctx, j); 			[2]

    if (!q->nr_hw_queues)					[3]
      goto err_hctxs;

  err_exit:
      q->mq_ops = NULL;			  			[4]

  blk_put_queue
    blk_release_queue
      if (queue_is_mq(q))					[5]
        blk_mq_release(q);

[1]: blk_mq_alloc_and_init_hctx failed at i != 0.
[2]: The hctxs allocated by [1] are moved to q->unused_hctx_list and
will be cleaned up in blk_mq_release.
[3]: q->nr_hw_queues is 0.
[4]: Set q->mq_ops to NULL.
[5]: queue_is_mq returns false due to [4]. And blk_mq_release
will not be called. The hctxs in q->unused_hctx_list are leaked.

To fix it, call blk_release_queue in exception path.