CVE-2024-39476

/// Technical description

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

md/raid5: fix deadlock that raid5d() wait for itself to clear MD_SB_CHANGE_PENDING

Xiao reported that lvm2 test lvconvert-raid-takeover.sh can hang with

small possibility, the root cause is exactly the same as commit

bed9e27baf52 ("Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"")

However, Dan reported another hang after that, and junxiao investigated

the problem and found out that this is caused by plugged bio can't issue

from raid5d().

Current implementation in raid5d() has a weird dependence:

1) md_check_recovery() from raid5d() must hold 'reconfig_mutex' to clear

MD_SB_CHANGE_PENDING;

2) raid5d() handles IO in a deadloop, until all IO are issued;

3) IO from raid5d() must wait for MD_SB_CHANGE_PENDING to be cleared;

This behaviour is introduce before v2.6, and for consequence, if other

context hold 'reconfig_mutex', and md_check_recovery() can't update

super_block, then raid5d() will waste one cp

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References