linux-kernel - Re: [PATCH v1] bcachefs: add check for btree id against max in try read node

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Message-ID: <lxq42z72rrcoqmcj6z4rvesjvxoxf3q7dss666pjyzao4gaftt@tiayr4siis3z>
Date: Sun, 6 Oct 2024 23:05:50 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Piotr Zalewski <pZ010001011111@...ton.me>
Cc: linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	skhan@...uxfoundation.org, syzbot+cf7b2215b5d70600ec00@...kaller.appspotmail.com
Subject: Re: [PATCH v1] bcachefs: add check for btree id against max in try
 read node

On Mon, Oct 07, 2024 at 02:53:13AM GMT, Piotr Zalewski wrote:
> > Add check for read node's btree_id against BTREE_ID_NR_MAX in
> > try_read_btree_node to prevent triggering EBUG_ON condition in
> > bch2_btree_id_root[1].
> 
> There seems to be some kind of (pro)regression regarding this issue. Now it
> triggers a deadlock. I also found related bug detected by syzbot[2] for
> which someone supplied the same patch recently and it triggered the same
> deadlock. I will look into it (perhaps simple check isn't a proper fix 
> here).
> 
> > [1] https://syzkaller.appspot.com/bug?extid=cf7b2215b5d70600ec00
> 
> [2] https://syzkaller.appspot.com/bug?extid=9f41e4b255897d99d4e9

Your patch looks correct, [2] shouldn't be possible with it - and it
appears to only be reported on upstream commits. I'll apply your patch.