md: wake raid456 reshape waiters before suspend

Overview

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

md: wake raid456 reshape waiters before suspend

During raid456 reshape, direct IO across the reshape position can sleep in raid5_make_request() waiting for reshape progress while still holding an active_io reference. If userspace then freezes reshape and writes md/suspend_lo or md/suspend_hi, mddev_suspend() kills active_io and waits for all in-flight IO to drain.

This can deadlock: the IO needs reshape progress to continue, but the reshape thread is already frozen, so the active_io reference is never dropped and suspend never completes.

raid5_prepare_suspend() already wakes wait_for_reshape for dm-raid. Do the same for normal md suspend when reshape is already interrupted, so waiting raid456 IO can abort, drop its reference, and let suspend finish.

The mdadm test tests/25raid456-reshape-deadlock reproduces the hang.

Affected

• Linux >= 714d20150ed85811193ae07a494d91f9927c590f < 8b6a72420821e6da2cab6a69d5233500d2698b93
• Linux >= 714d20150ed85811193ae07a494d91f9927c590f < ff6b93410192b812d73cc54062529715b2dc849f
• Linux >= 714d20150ed85811193ae07a494d91f9927c590f < 8ae3e14d7f3df58f7f49c02d74344e3dcd5f84f0
• Linux >= 714d20150ed85811193ae07a494d91f9927c590f < cf86bb53b9c92354904a328e947a05ffbfdd1840
• Linux 2284eab166f2df83f94f0422e15dc9e73b278abf
• Linux >= 6.6.160 < 6.7
• Linux 6.7

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.