Re: [PATCH 134/190] Revert "md: Fix failed allocation of md_register_thread"

[Song Liu]

> On Apr 27, 2021, at 10:46 PM, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> 
> On Wed, Apr 21, 2021 at 03:00:09PM +0200, Greg Kroah-Hartman wrote:
>> This reverts commit e406f12dde1a8375d77ea02d91f313fb1a9c6aec.
>> 
>> Commits from @umn.edu addresses have been found to be submitted in "bad
>> faith" to try to test the kernel community's ability to review "known
>> malicious" changes.  The result of these submissions can be found in a
>> paper published at the 42nd IEEE Symposium on Security and Privacy
>> entitled, "Open Source Insecurity: Stealthily Introducing
>> Vulnerabilities via Hypocrite Commits" written by Qiushi Wu (University
>> of Minnesota) and Kangjie Lu (University of Minnesota).
>> 
>> Because of this, all submissions from this group must be reverted from
>> the kernel tree and will need to be re-reviewed again to determine if
>> they actually are a valid fix.  Until that work is complete, remove this
>> change to ensure that no problems are being introduced into the
>> codebase.
>> 
>> Cc: stable@xxxxxxxxxxxxxxx # v3.16+
>> Cc: Guoqing Jiang <gqjiang@xxxxxxxx>
>> Cc: Aditya Pakki <pakki001@xxxxxxx>
>> Cc: Song Liu <songliubraving@xxxxxx>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>> ---
>> drivers/md/raid10.c | 2 --
>> drivers/md/raid5.c  | 2 --
>> 2 files changed, 4 deletions(-)
>> 
>> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
>> index a9ae7d113492..4fec1cdd4207 100644
>> --- a/drivers/md/raid10.c
>> +++ b/drivers/md/raid10.c
>> @@ -3896,8 +3896,6 @@ static int raid10_run(struct mddev *mddev)
>> 		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
>> 		mddev->sync_thread = md_register_thread(md_do_sync, mddev,
>> 							"reshape");
>> -		if (!mddev->sync_thread)
>> -			goto out_free_conf;
>> 	}
>> 
>> 	return 0;
>> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>> index 5d57a5bd171f..9b2bd50beee7 100644
>> --- a/drivers/md/raid5.c
>> +++ b/drivers/md/raid5.c
>> @@ -7677,8 +7677,6 @@ static int raid5_run(struct mddev *mddev)
>> 		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
>> 		mddev->sync_thread = md_register_thread(md_do_sync, mddev,
>> 							"reshape");
>> -		if (!mddev->sync_thread)
>> -			goto abort;
>> 	}
>> 
>> 	/* Ok, everything is just fine now */
>> -- 
>> 2.31.1
>> 
> 
> These changes look ok, but the error handling logic seems to be freeing
> the incorrect thread, not the one that these functions create.  That's
> independant of this change, but seems odd.  If someone cares about it,
> it should probably be looked at, or if correct, a comment would be nice
> as it's really confusing.

I don't think this is confusing. raid[5|10]_run() creates two threads:
first mddev->thread, then mddev->sync_thread. If we fail to create the
second thread (sync_thread), we free the first thread (mddev->thread) in 
the error handling logic. 

Thanks,
Song