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CVE-2024-38598: md: fix resync softlockup when bitmap size is less than array size

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.

Affected products

How to fix

Upgrade to a fixed version: Linux kernel 4.19.316, 5.10.219, 5.15.161, 5.4.278. Check the vendor advisory for mitigations.

References

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