linux-kernel - Re: [PATCH] hfs: Sanity check the root record

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Message-ID: <20241126215254.aw7l7k3tgx2tawzu@quack3>
Date: Tue, 26 Nov 2024 22:52:54 +0100
From: Jan Kara <jack@...e.cz>
To: Leo Stone <leocstone@...il.com>
Cc: Jan Kara <jack@...e.cz>,
	syzbot+2db3c7526ba68f4ea776@...kaller.appspotmail.com,
	brauner@...nel.org, quic_jjohnson@...cinc.com,
	viro@...iv.linux.org.uk, sandeen@...hat.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com, shuah@...nel.org,
	anupnewsmail@...il.com,
	linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] hfs: Sanity check the root record

On Tue 26-11-24 09:21:50, Leo Stone wrote:
> Hello,
> 
> On Tue, Nov 26, 2024 at 10:33:13AM +0100, Jan Kara wrote:
> > 
> > This certainly won't hurt but shouldn't we also add some stricter checks
> > for entry length so that we know we've loaded enough data to have full info
> > about the root dir?
> 
> Yes, that would be a good idea. Do we want to keep the existing checks
> and just make sure we have at least enough to initialize the struct:
> 
> if (fd.entrylength > sizeof(rec) || fd.entrylength < 0 ||
>     fd.entrylength < sizeof(rec.dir)) {
> 	res = -EIO;
> 	goto bail_hfs_find;
> }
> 
> Or be even stricter and only accept the exact length:
> 
> if (fd.entrylength != sizeof(rec.dir)) {
> 	res = -EIO;
> 	goto bail_hfs_find;
> }

Yes, this strict check would make sense to me. I just don't know HFS good
enough whether this is a safe assumption to make so it would be good to
test with some HFS filesystem.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR