linux-kernel - Re: [PATCH v4 1/1] scsi: ufs: core: add device level exception support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <3d7b543c-1165-42e0-8471-25b04c7572ac@acm.org>
Date: Thu, 27 Mar 2025 07:36:56 -0400
From: Bart Van Assche <bvanassche@....org>
To: "Bao D. Nguyen" <quic_nguyenb@...cinc.com>,
 Arthur Simchaev <Arthur.Simchaev@...disk.com>,
 "quic_cang@...cinc.com" <quic_cang@...cinc.com>,
 "quic_nitirawa@...cinc.com" <quic_nitirawa@...cinc.com>,
 "avri.altman@....com" <avri.altman@....com>,
 "peter.wang@...iatek.com" <peter.wang@...iatek.com>,
 "manivannan.sadhasivam@...aro.org" <manivannan.sadhasivam@...aro.org>,
 "minwoo.im@...sung.com" <minwoo.im@...sung.com>,
 "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
 "martin.petersen@...cle.com" <martin.petersen@...cle.com>
Cc: "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
 Alim Akhtar <alim.akhtar@...sung.com>,
 "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Bean Huo <beanhuo@...ron.com>, Keoseong Park <keosung.park@...sung.com>,
 Ziqi Chen <quic_ziqichen@...cinc.com>, Al Viro <viro@...iv.linux.org.uk>,
 Gwendal Grignou <gwendal@...omium.org>, Eric Biggers <ebiggers@...gle.com>,
 open list <linux-kernel@...r.kernel.org>,
 "moderated list:ARM/Mediatek SoC support:Keyword:mediatek"
 <linux-arm-kernel@...ts.infradead.org>,
 "moderated list:ARM/Mediatek SoC support:Keyword:mediatek"
 <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v4 1/1] scsi: ufs: core: add device level exception
 support

On 3/26/25 7:47 PM, Bao D. Nguyen wrote:
> On 3/26/2025 3:49 AM, Bart Van Assche wrote:
>> On 3/25/25 6:15 PM, Bao D. Nguyen wrote:
>>> The existing "struct utp_upiu_query_v4_0" probably has a bug in it. 
>>> It does not use the  __attribute__((__packed__)) attribute. The 
>>> compiler is free to add padding in this structure, resulting in the 
>>> read attribute value being incorrect. I plan to provide a separate 
>>> patch to fix this issue.
>>
>> Adding __attribute__((__packed__)) or __packed to data structures that
>> don't need it is not an improvement but is a change that makes
>> processing slower on architectures that do not support unaligned
>> accesses. Instead of adding __packed to data structures in their
>> entirety, only add it to those members that need it and check the
>> structure size as follows:
>>
>> static_assert(sizeof(...) == ...);
>>
> Thank you for the info on this, Bart.
> IMO, this response upiu data should be __packed because the data coming 
> from the hardware follows a strict format as defined by the spec. If we 
> support __pack each individual field which data may be read by the 
> driver (the attribute read commands) and check the validity of their 
> sizes, it may add some complexity?

Hi Bao,

As explained in my previous email, adding __packed to data structures in
their entirety is a bad practice. Please don't do this.

Regarding your question: I have not yet seen any data structure that
represents an on-the-wire data format where every single data member
has to be annotated with __packed. Only data members that are not
aligned to a natural boundary need this annotation. Examples are
available in this header file: include/scsi/srp.h.

Thanks,

Bart.