CVE-2024-38598 md: fix resync softlockup when bitmap size is less than array size
A logic error in the Linux kernel's md/raid10 resync process causes a CPU soft lockup, leading to a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-38598?
CVE-2024-38598 is a medium-severity denial of service vulnerability in Linux kernel, published on 19 Jun 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-667
Which versions are affected by CVE-2024-38598?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-38598?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-38598 being exploited?
There is no known exploitation of CVE-2024-38598 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-38598, DEBIAN-CVE-2024-38598, GHSA-c8cc-57pq-936r, UBUNTU-CVE-2024-38598.