CVE-2024-38598

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.