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

md: fix resync softlockup when bitmap size is less than array size

Is is reported that for dm-raid10, lvextend + lvchange --syncaction will
trigger following softlockup:

kernel:watchdog: BUG: soft lockup - CPU#3 stuck for 26s! [mdX_resync:6976]
CPU: 7 PID: 3588 Comm: mdX_resync Kdump: loaded Not tainted 6.9.0-rc4-next-20240419 #1
RIP: 0010:_raw_spin_unlock_irq+0x13/0x30
Call Trace:
 <TASK>
 md_bitmap_start_sync+0x6b/0xf0
 raid10_sync_request+0x25c/0x1b40 [raid10]
 md_do_sync+0x64b/0x1020
 md_thread+0xa7/0x170
 kthread+0xcf/0x100
 ret_from_fork+0x30/0x50
 ret_from_fork_asm+0x1a/0x30

And the detailed process is as follows:

md_do_sync
 j = mddev->resync_min
 while (j < max_sectors)
  sectors = raid10_sync_request(mddev, j, &skipped)
   if (!md_bitmap_start_sync(..., &sync_blocks))
    // md_bitmap_start_sync set sync_blocks to 0
    return sync_blocks + sectors_skippe;
  // sectors = 0;
  j += sectors;
  // j never change

Root cause is that commit 301867b1c168 ("md/raid10: check
slab-out-of-bounds in md_bitmap_get_counter") return early from
md_bitmap_get_counter(), without setting returned blocks.

Fix this problem by always set returned blocks from
md_bitmap_get_counter"(), as it used to be.

Noted that this patch just fix the softlockup problem in kernel, the
case that bitmap size doesn't match array size still need to be fixed.

kernel.org https://git.kernel.org/stable/c/3f5b73ef8fd6268cbc968b308d8eafe56fda97f3 [No types assigned]

kernel.org https://git.kernel.org/stable/c/43771597feba89a839c5f893716df88ae5c237ce [No types assigned]

kernel.org https://git.kernel.org/stable/c/5817f43ae1a118855676f57ef7ab50e37eac7482 [No types assigned]

kernel.org https://git.kernel.org/stable/c/69296914bfd508c85935bf5f711cad9b0fe78492 [No types assigned]

kernel.org https://git.kernel.org/stable/c/71e8e4f288e74a896b6d9cd194f3bab12bd7a10f [No types assigned]

kernel.org https://git.kernel.org/stable/c/8bbc71315e0ae4bb7e37f8d43b915e1cb01a481b [No types assigned]

kernel.org https://git.kernel.org/stable/c/c9566b812c8f66160466cc1e29df6d3646add0b1 [No types assigned]

kernel.org https://git.kernel.org/stable/c/d4b9c764d48fa41caa24cfb4275f3aa9fb4bd798 [No types assigned]

kernel.org https://git.kernel.org/stable/c/f0e729af2eb6bee9eb58c4df1087f14ebaefe26b [No types assigned]