Home Assistant DOS’ed my NAS

Posting this because I had a hard time finding it elsewhere, and wanted to boost the visibility.

Tried to log in to my Synology NAS tonight and got a message that said “You can’t, the disk is full.” Seemed unlikely to me, I had just been logged in earlier and had a terabyte available. I generate a lot of crap, but a terabyte in less than a day seemed suspicious.

I was able to get in via SSH, poked around. The /volume1 folder still had plenty of free space, so I began poking into the rest of the folders. Most were maybe a few Mb… but var was 900Mb. I dig down a few layers and get to /var/lib/synosmartblock was most of it. A few places on the net said it was safe to delete that, and the problem would go away after a reboot. SO, I tried and it did.

All good, right?

I reboot, log in through the web UI and notice everything is slooow. CPU in 99%. Hm. Back to SSH, back to synosmartblock. It’s huge again. Something is clearly causing it. I take a look at the results of ps -A.

There’s what can only be described as a shit ton of processes running. And a lot of them are auth.cgi. My NAS is not exposed outside my home network, so I’m thinking it’s not hackers. (I hope not, at least.) A search for synology and auth.cgi turns up this link:

100% cpu, bunch of auth.cgi : synology – Reddit

Yeah, that sounds right. And the redditor noted it was Home Assistant having lost it’s mind and decided to ping the NAS for status. Damn near continuously. The NAS couldn’t keep up and filled its system folders. And, since Home Assistant was waiting for a response on each request, it too was inaccessible. Reboot, remove the Synology integration in Home Assistant and we’re happy again.

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