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

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Message-ID: <wzxs6mjqlpf2eszoaw2ozvocqg3lpaqx7mzog4tygxexugrbsu@3pxs2vthfagb>
Date: Tue, 26 Nov 2024 09:21:50 -0800
From: Leo Stone <leocstone@...il.com>
To: Jan Kara <jack@...e.cz>
Cc: 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

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;
}

Thanks for your feedback,
Leo