linux-kernel - Re: [PATCH 0/1] hfs: discuss to add offset/length validation in hfs_brec

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Message-ID: <ee40295987f48507fd1a0621f91d952a3ee2f9a4.camel@ibm.com>
Date: Mon, 18 Aug 2025 17:59:03 +0000
From: Viacheslav Dubeyko <Slava.Dubeyko@....com>
To: "glaubitz@...sik.fu-berlin.de" <glaubitz@...sik.fu-berlin.de>,
        "yang.chenzhi@...o.com" <yang.chenzhi@...o.com>,
        "slava@...eyko.com"
	<slava@...eyko.com>,
        "frank.li@...o.com" <frank.li@...o.com>
CC: "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re:  [PATCH 0/1] hfs: discuss to add offset/length validation in
 hfs_brec_lenoff

On Mon, 2025-08-18 at 22:17 +0800, Chenzhi Yang wrote:
> From: Yang Chenzhi <yang.chenzhi@...o.com>
> 
> When running syzbot with a crafted HFS/HFS+ disk image containing
> invalid record offsets or lengths, the filesystem may hang. For
> example, in this case syzbot set the header’s second record offset
> to 0x7f00 while node_size is 4096. HFS/HFS+ failed to detect this
> fault, which eventually led to a crash.
> 

HFS has 512 bytes b-tree node size.

> Since HFS/HFS+ makes heavy use of hfs_brec_lenoff, adding manual
> offset/length checks at every call site would be tedious and
> error-prone.
> 

You are mentioning HFS here. But you've shared fix only for HFS+. Are you
planning to share the fix for HFS too?

Thanks,
Slava.

> Instead, it may be more robust to introduce validation directly
> inside hfs_brec_lenoff (or at a similar central point), ensuring
> that all callers can safely rely on the returned offset and length
> without additional checks.
> 
> Yang Chenzhi (1):
>   hfs: validate record offset in hfsplus_bmap_alloc
> 
>  fs/hfsplus/bnode.c      | 41 ----------------------------------------
>  fs/hfsplus/btree.c      |  6 ++++++
>  fs/hfsplus/hfsplus_fs.h | 42 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 48 insertions(+), 41 deletions(-)