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PUBLISHED

CVE-2024-26757

md: Don't ignore read-only array in md_check_recovery()

Reserved:2024-02-19
Published:2024-04-03
Updated:2024-04-04

Description

In the Linux kernel, the following vulnerability has been resolved: md: Don't ignore read-only array in md_check_recovery() Usually if the array is not read-write, md_check_recovery() won't register new sync_thread in the first place. And if the array is read-write and sync_thread is registered, md_set_readonly() will unregister sync_thread before setting the array read-only. md/raid follow this behavior hence there is no problem. After commit f52f5c71f3d4 ("md: fix stopping sync thread"), following hang can be triggered by test shell/integrity-caching.sh: 1) array is read-only. dm-raid update super block: rs_update_sbs ro = mddev->ro mddev->ro = 0 -> set array read-write md_update_sb 2) register new sync thread concurrently. 3) dm-raid set array back to read-only: rs_update_sbs mddev->ro = ro 4) stop the array: raid_dtr md_stop stop_sync_thread set_bit(MD_RECOVERY_INTR, &mddev->recovery); md_wakeup_thread_directly(mddev->sync_thread); wait_event(..., !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) 5) sync thread done: md_do_sync set_bit(MD_RECOVERY_DONE, &mddev->recovery); md_wakeup_thread(mddev->thread); 6) daemon thread can't unregister sync thread: md_check_recovery if (!md_is_rdwr(mddev) && !test_bit(MD_RECOVERY_NEEDED, &mddev->recovery)) return; -> -> MD_RECOVERY_RUNNING can't be cleared, hence step 4 hang; The root cause is that dm-raid manipulate 'mddev->ro' by itself, however, dm-raid really should stop sync thread before setting the array read-only. Unfortunately, I need to read more code before I can refacter the handler of 'mddev->ro' in dm-raid, hence let's fix the problem the easy way for now to prevent dm-raid regression.

Product status

Default status
unaffected

ecbfb9f118bc before 2ea169c5a0b1
affected

ecbfb9f118bc before 55a48ad2db64
affected

Default status
affected

4.8
affected

Any version before 4.8
unaffected

6.7.7
unaffected

6.8
unaffected

References

https://git.kernel.org/stable/c/2ea169c5a0b1134d573d07fc27a16f327ad0e7d3

https://git.kernel.org/stable/c/55a48ad2db64737f7ffc0407634218cc6e4c513b

cve.org CVE-2024-26757

nvd.nist.gov CVE-2024-26757

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