CVE-2022-49901

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

blk-mq: Fix kmemleak in blkmqinitallocatedqueue

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>] kmallocnodetrace+0x22/0x60 [<00000000648f7950>] blkmqallocandinithctx+0x289/0x350 [<00000000af06de0e>] blkmqreallochwctxs+0x2fe/0x3d0 [<00000000e00c1872>] blkmqinitallocatedqueue+0x48c/0x1440 [<00000000d16b4e68>] _blkmqallocdisk+0xc8/0x1c0 [<00000000d10c98c3>] 0xffffffffc450d69d [<00000000b9299f48>] 0xffffffffc4538392 [<0000000061c39ed6>] dooneinitcall+0xd0/0x4f0 [<00000000b389383b>] doinitmodule+0x1a4/0x680 [<0000000087cf3542>] loadmodule+0x6249/0x7110 [<00000000beba61b8>] _dosysfinitmodule+0x140/0x200 [<00000000fdcfff51>] dosyscall64+0x35/0x80 [<000000003c0f1f71>] entrySYSCALL64afterhwframe+0x46/0xb0

That is because q->maops is set to NULL before blkrelease_queue is called.

blkmqinitqueuedata blkmqinitallocatedqueue blkmqreallochwctxs for (i = 0; i < set->nrhwqueues; i++) { oldhctx = xaload(&q->hctxtable, i); if (!blkmqallocandinithctx(.., 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;

errexit: q->mqops = NULL; [4]

blkputqueue blkreleasequeue if (queueismq(q)) [5] blkmqrelease(q);

will be cleaned up in blkmqrelease. will not be called. The hctxs in q->unusedhctxlist are leaked.

To fix it, call blkreleasequeue in exception path.