Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Content-Type: text/plain;
        charset=utf-8
Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.20.0.2.21\))
Subject: Re: [PATCH v1] qnx4_match: do not over run the buffer
From:   Tong Zhang <ztong0001@gmail.com>
In-Reply-To: <1645927.Y8UaVx19Bi@alarsen.net>
Date:   Sat, 21 Nov 2020 20:27:37 -0500
Cc:     linux-kernel@vger.kernel.org
Content-Transfer-Encoding: quoted-printable
Message-Id: <97DE78A8-E2D6-4780-AD77-5F679D6DE098@gmail.com>
References: <20201120212120.2502522-1-ztong0001@gmail.com>
 <2474566.rpppqFFLNx@alarsen.net>
 <E554952E-602B-4711-BEF1-FB3398DA7225@gmail.com>
 <1645927.Y8UaVx19Bi@alarsen.net>
To:     Anders Larsen <al@alarsen.net>
Precedence: bulk

Thanks for the clarification! This sounds good to me.
I will send a revised patch.
Best,
- Tong

> On Nov 21, 2020, at 4:57 PM, Anders Larsen <al@alarsen.net> wrote:
>=20
> On Saturday, 2020-11-21 22:47 Tong Zhang wrote:
>>=20
>>> On Nov 21, 2020, at 4:40 PM, Anders Larsen <al@alarsen.net> wrote:
>>>=20
>>> On Friday, 2020-11-20 22:21 Tong Zhang wrote:
>>>> the di_fname may not terminated by '\0', use strnlen to prevent =
buffer
>>>> overrun
>>>>=20
>>>> ---
>>>> fs/qnx4/namei.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>=20
>>>> diff --git a/fs/qnx4/namei.c b/fs/qnx4/namei.c
>>>> index 8d72221735d7..c0e79094f578 100644
>>>> --- a/fs/qnx4/namei.c
>>>> +++ b/fs/qnx4/namei.c
>>>> @@ -40,7 +40,7 @@ static int qnx4_match(int len, const char *name,
>>>> 	} else {
>>>> 		namelen =3D QNX4_SHORT_NAME_MAX;
>>>> 	}
>>>> -	thislen =3D strlen( de->di_fname );
>>>> +	thislen =3D strnlen( de->di_fname, QNX4_SHORT_NAME_MAX );
>>>=20
>>> that should be
>>> +	thislen =3D strnlen( de->di_fname, namelen );
>>> otherwise the length of a filename would always be limited to =
QNX4_SHORT_NAME_MAX (16) characters.
>>>=20
>> Why should we put something bigger here if the size of =
qnx4_inode_entry->di_fname is QNX4_SHORT_NAME_MAX.
>> Won=E2=80=99t that be a problem?
>=20
> If QNX4_FILE_LINK is set in de->di_status (see line 38), 'de' actually =
points to a struct qnx4_link_info which can hold a longer name.
> That's the reason for the namelen massage.
> (Please don't ask why it is not a union)
>=20
> Cheers
> Anders
>=20
>=20