linux-kernel - Re: [PATCH v4] staging: rtl8723bs: Use % 4096u instead of & 0xfff

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: <CADYq+fZ0uDxZg2SjqLJfjSY1EG9E16gHRouknqt8k-1HZqfh=A@mail.gmail.com>
Date: Mon, 7 Apr 2025 09:07:49 +0100
From: Samuel Abraham <abrahamadekunle50@...il.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: gregkh@...uxfoundation.org, julia.lawall@...ia.fr, 
	outreachy@...ts.linux.dev, linux-staging@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, andy@...nel.org, david.laight.linux@...il.com
Subject: Re: [PATCH v4] staging: rtl8723bs: Use % 4096u instead of & 0xfff

On Mon, Apr 7, 2025 at 8:20 AM Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> On Mon, Apr 07, 2025 at 06:30:50AM +0000, Abraham Samuel Adekunle wrote:
> > The sequence number is constrained to a range of [0, 4095], which
> > is a total of 4096 values. The bitmask operation using `0xfff` is
> > used to perform this wrap-around. While this is functionally correct,
> > it obscures the intended semantic of a 4096-based wrap.
> >
> > Using a modulo operation with `4096u` makes the wrap-around logic
> > explicit and easier to understand. It clearly signals that the sequence
> > number cycles though a range of 4096 values.
> > It also makes the code robust against potential changes of the 4096
> > upper limit, especially when it becomes a non power of 2 value while
> > the AND(&) works solely for power of 2 values.
> >
> > The use of `4096u` also guarantees that the modulo operation is performed
> > with unsigned arithmetic, preventing potential issues with signed types.
> >
> > Suggested-by: Andy Shevchenko <andy@...nel.org>
> > Signed-off-by: Abraham Samuel Adekunle <abrahamadekunle50@...il.com>
> > ---
> > Changes in v3:
> >       - Added more description to the commit message
> >       - Removed blank line in tag block.
> >       -  Added more patch recipients.
> > Changes in v2:
> >       - Changed the commit message to a more descriptive message which
> >       makes it clear why the patch does the change.
> >       - Changed the subject title to include `4096u` to show that an unsigned
> >       module is used.
> > Changes in v1:
> >       - Added more patch recipients.
> >
> >  drivers/staging/rtl8723bs/core/rtw_xmit.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/staging/rtl8723bs/core/rtw_xmit.c b/drivers/staging/rtl8723bs/core/rtw_xmit.c
> > index 297c93d65315..f534bf2448c3 100644
> > --- a/drivers/staging/rtl8723bs/core/rtw_xmit.c
> > +++ b/drivers/staging/rtl8723bs/core/rtw_xmit.c
> > @@ -943,7 +943,7 @@ s32 rtw_make_wlanhdr(struct adapter *padapter, u8 *hdr, struct pkt_attrib *pattr
> >
> >                       if (psta) {
> >                               psta->sta_xmitpriv.txseq_tid[pattrib->priority]++;
> > -                             psta->sta_xmitpriv.txseq_tid[pattrib->priority] &= 0xFFF;
> > +                             psta->sta_xmitpriv.txseq_tid[pattrib->priority] &= 4096u;
>
> You forgot to change the & to %.

Thank you very much, Dan. I will correct and resend the patch.

Adekunle