Subject: Re: [Patch net] net: remove the bogus overflow debug check in pskb_may_pull()

From: Florian Westphal <[email-masked]>
Date: Fri, 7 Jun 2024 01:27:47 +0200

Cong Wang <[email-masked]> wrote:
> From: Cong Wang <[email-masked]>
> 
> Commit 219eee9c0d16 ("net: skbuff: add overflow debug check to pull/push
> helpers") introduced an overflow debug check for pull/push helpers.
> For __skb_pull() this makes sense because its callers rarely check its
> return value. But for pskb_may_pull() it does not make sense, since its
> return value is properly taken care of. Remove the one in
> pskb_may_pull(), we can continue rely on its return value.

See 025f8ad20f2e3264d11683aa9cbbf0083eefbdcd which would not exist
without this check, I would not give up yet.

bpf_try_make_writable() could do an explicit check vs. skb->len.

If anyone needs it, splat is at
https://syzkaller.appspot.com/bug?extid=0c4150bff9fff3bf023c