In the Linux kernel, the following vulnerability has been resolved:
md: Dont suspend the array for interrupted reshape
md_start_sync() will suspend the array if there are spares that can be added or removed from conf, however, if reshape is still in progress, this wont happen at all or data will be corrupted(remove_and_add_spares wont be called from md_choose_sync_action for reshape), hence there is no need to suspend the array if reshape is not done yet.
Meanwhile, there is a potential deadlock for raid456:
reshape is interrupted;
set one of the disk WantReplacement, and add a new disk to the array, however, recovery wont start until the reshape is finished;
then issue an IO across reshpae position, this IO will wait for reshape to make progress;
continue to reshape, then md_start_sync() found there is a spare disk that can be added to conf, mddev_suspend() is called;
Step 4 and step 3 is waiting for each other, deadlock triggered. Noted this problem is found by code review, and its not reporduced yet.
Fix this porblem by dont suspend the array for interrupted reshape, this is safe because conf wont be changed until reshape is done.