Re: [PATCH net-next] net: fix up truesize of cloned skb in skb_prepare_for_shift()

On Mon, Feb 1, 2021 at 6:34 PM Marco Elver [off-list ref] wrote:

On Mon, 1 Feb 2021 at 17:50, Christoph Paasch

quoted

just a few days ago we found out that this also fixes a syzkaller
issue on MPTCP (https://github.com/multipath-tcp/mptcp_net-next/issues/136).
I confirmed that this patch fixes the issue for us as well:

Tested-by: Christoph Paasch <redacted>

That's interesting, because according to your config you did not have
KFENCE enabled. Although it's hard to say what exactly caused the
truesize mismatch in your case, because it clearly can't be KFENCE
that caused ksize(kmalloc(S))!=ksize(kmalloc(S)) for you.

Indeed, this seems strange. This might be a different issue.

Maybe S != S ;)