CVE-2024-26962 Information

May 04, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

dm-raid456 md/raid456: fix a deadlock for dm-raid456 while io concurrent with reshape

For raid456 if reshape is still in progress then IO across reshape position will wait for reshape to make progress. However for dm-raid in following cases reshape will never make progress hence IO will hang:

  1. the array is read-only;
  2. MD_RECOVERY_WAIT is set;
  3. MD_RECOVERY_FROZEN is set;

After commit c467e97f079f (\md/raid6: use valid sector values to determine if an I/O should wait on the reshape) fix the problem that IO across reshape position doesn’t wait for reshape the dm-raid test shell/lvconvert-raid-reshape.sh start to hang:

[root@fedora ~] cat /proc/979/stack [<0>] wait_woken+0x7d/0x90 [<0>] raid5_make_request+0x929/0x1d70 [raid456] [<0>] md_handle_request+0xc2/0x3b0 [md_mod] [<0>] raid_map+0x2c/0x50 [dm_raid] [<0>] __map_bio+0x251/0x380 [dm_mod] [<0>] dm_submit_bio+0x1f0/0x760 [dm_mod] [<0>] __submit_bio+0xc2/0x1c0 [<0>] submit_bio_noacct_nocheck+0x17f/0x450 [<0>] submit_bio_noacct+0x2bc/0x780 [<0>] submit_bio+0x70/0xc0 [<0>] mpage_readahead+0x169/0x1f0 [<0>] blkdev_readahead+0x18/0x30 [<0>] read_pages+0x7c/0x3b0 [<0>] page_cache_ra_unbounded+0x1ab/0x280 [<0>] force_page_cache_ra+0x9e/0x130 [<0>] page_cache_sync_ra+0x3b/0x110 [<0>] filemap_get_pages+0x143/0xa30 [<0>] filemap_read+0xdc/0x4b0 [<0>] blkdev_read_iter+0x75/0x200 [<0>] vfs_read+0x272/0x460 [<0>] ksys_read+0x7a/0x170 [<0>] __x64_sys_read+0x1c/0x30 [<0>] do_syscall_64+0xc6/0x230 [<0>] entry_SYSCALL_64_after_hwframe+0x6c/0x74

This is because reshape can’t make progress.

For md/raid the problem doesn’t exist because register new sync_thread doesn’t rely on the IO to be done any more:

  1. If array is read-only it can switch to read-write by ioctl/sysfs;
  2. md/raid never set MD_RECOVERY_WAIT;
  3. If MD_RECOVERY_FROZEN is set mddev_suspend() doesn’t hold ‘reconfig_mutex’ hence it can be cleared and reshape can continue by sysfs api ‘sync_action’.

However I’m not sure yet how to avoid the problem in dm-raid yet. This patch on the one hand make sure raid_message() can’t change sync_thread() through raid_message() after presuspend() on the other hand detect the above 3 cases before wait for IO do be done in dm_suspend() and let dm-raid requeue those IO.

Reference

https://git.kernel.org/stable/c/5943a34bf6bab5801e08a55f63e1b8d5bc90dae1 https://git.kernel.org/stable/c/a8d249d770cb357d16a2097b548d2e4c1c137304 https://git.kernel.org/stable/c/41425f96d7aa59bc865f60f5dda3d7697b555677

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