CVE-2024-35794

In the Linux kernel, the following vulnerability has been resolved:
dm-raid: really frozen sync_thread during suspend 1) commit f52f5c71f3d4
(“md: fix stopping sync thread”) remove MD_RECOVERY_FROZEN from
__md_stop_writes() and doesn’t realize that dm-raid relies on
__md_stop_writes() to frozen sync_thread indirectly. Fix this problem by
adding MD_RECOVERY_FROZEN in md_stop_writes(), and since stop_sync_thread()
is only used for dm-raid in this case, also move stop_sync_thread() to
md_stop_writes(). 2) The flag MD_RECOVERY_FROZEN doesn’t mean that sync
thread is frozen, it only prevent new sync_thread to start, and it can’t
stop the running sync thread; In order to frozen sync_thread, after seting
the flag, stop_sync_thread() should be used. 3) The flag MD_RECOVERY_FROZEN
doesn’t mean that writes are stopped, use it as condition for
md_stop_writes() in raid_postsuspend() doesn’t look correct. Consider that
reentrant stop_sync_thread() do nothing, always call md_stop_writes() in
raid_postsuspend(). 4) raid_message can set/clear the flag
MD_RECOVERY_FROZEN at anytime, and if MD_RECOVERY_FROZEN is cleared while
the array is suspended, new sync_thread can start unexpected. Fix this by
disallow raid_message() to change sync_thread status during suspend. Note
that after commit f52f5c71f3d4 (“md: fix stopping sync thread”), the test
shell/lvconvert-raid-reshape.sh start to hang in stop_sync_thread(), and
with previous fixes, the test won’t hang there anymore, however, the test
will still fail and complain that ext4 is corrupted. And with this patch,
the test won’t hang due to stop_sync_thread() or fail due to ext4 is
corrupted anymore. However, there is still a deadlock related to dm-raid456
that will be fixed in following patches.