BUG: XCM transfer, that would slash account leads to total asset loss.

[dudo50]

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• This is not a support question.

Description of bug

There is huge bug, where, when account tries to transfer XCM Message that will also slash dust (cause to go below existential deposit) their account, the account will suffer total asset loss and XCM message will not get sent. This only occurs on Kusama Asset Hub, Polkadot works fine, because it does not have latest runtime.

Steps to reproduce

Transfer amount that will result in less than existential deposit on Kusama Asset Hub (Kusama untested as I have verified identity there and do not want to loose it).

Or try any Kusama DEX and try transfer MAX option. (Kusama Asset Hub -> Kusama)

Other XCM transfers work as expected. Please, fix this bug as it could lead to huge asset losses if released on Polkadot also.

[KiChjang]

Which functionality did you use to transfer assets? Was it a teleport, or did you create your own XCM program? If it's the latter, can you show us your XCM program?

[dudo50]

Which functionality did you use to transfer assets? Was it a teleport, or did you create your own XCM program? If it's the latter, can you show us your XCM program?

Hey @KiChjang , we used native PolkadotXCM and limited teleport function.

Here is how the message was formatted (other messages that are formatted the same but would not slash account (amount remaining in the account after XCM is more than existential deposit) work just fine)

[ggwpez]

Apparently its this block: https://assethub-kusama.subscan.io/block/6284878?tab=event
And this state diff: diff.html.txt

[kianenigma]

I tried to emulate this issue using Chopsticks and at first attempt couldn't. Are you claiming that any teleport that leaves the sender below existential deposit on the kusama relay chain will cause a trap? I moved 5 KSM To Charlie, teleported 4.999999 to Charlie on AH and the teleport failed with a reasonable outcome, without any traps or loss of funds.

[dudo50]

@kianenigma If I understand you correctly, you tried Kusama -> AssetHub transfer. We encountered the issue on AssetHub->Kusama transfer.

[dudo50]

I am still able to recreate it, so it was not temporary: https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fkusama-asset-hub-rpc.polkadot.io#/explorer/query/0xd3191feabfc50b1c6415f2fd70cd704d77e3a61558e15721d20baf874732fcc6

https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fkusama-asset-hub-rpc.polkadot.io#/extrinsics/decode/0x8d02840084fc49ce30071ea611731838cc7736113c1ec68fbc47119be8a0805066df9b2b01988575310511e1dc64f6a1d041d9ca0be73beaf8c90c04f5949d89cbdefaf2768990d1c4853db0f4492eac27410aba4f7b2a87d46b918c49267086dc3402278b04018800001f09030100030001010084fc49ce30071ea611731838cc7736113c1ec68fbc47119be8a0805066df9b2b030400010000075ab2966e0b0000000000

[NachoPal]

I tried a limitedTeleport from AssetHubKusama to Kusama with Chopsticks and it worked.

Some edge case should be triggering the issue for your case.

Sorry, I read again the issue, I see what's the edge case

[NachoPal]

Can you share what was your balance when you tried to do the teleport and how much KSM you tried to teleport?

Not sure if I understand the issue, I am not able to reproduce it. I tried to teleport all my balance and it failed because a fee has to be paid beforehand. However, the sending account does not lose all its balance, just the mentioned fee.

[dudo50]

You can find my approximate balance here:
Around 0.04ksm. https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fkusama-asset-hub-rpc.polkadot.io#/extrinsics/decode/0x8d02840084fc49ce30071ea611731838cc7736113c1ec68fbc47119be8a0805066df9b2b01988575310511e1dc64f6a1d041d9ca0be73beaf8c90c04f5949d89cbdefaf2768990d1c4853db0f4492eac27410aba4f7b2a87d46b918c49267086dc3402278b04018800001f09030100030001010084fc49ce30071ea611731838cc7736113c1ec68fbc47119be8a0805066df9b2b030400010000075ab2966e0b0000000000

[dudo50]

Can you share what was your balance when you tried to do the teleport and how much KSM you tried to teleport?

Not sure if I understand the issue, I am not able to reproduce it. I tried to teleport all my balance and it failed because a fee has to be paid beforehand. However, the sending account does not lose all its balance, just the mentioned fee.

What was the call you used and how much was your balance/you tried to send? We are always sending amount-xcmfee*1.5. Not the entire amount because then it would fail as expected with inability to pay for fees.

[dudo50]

If you go to any dex, for eg Karura or Basilisk and go to cross-chain section and hit transfer max button for transferring KSM from KusamaAssetHub->Kusama you should be able to replicate. Be sure to not have lots of coins though.