linux-kernel - RE: [PATCH 2/6] treewide: remove using list iterator after loop body as a ptr

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]

Date:   Tue, 1 Mar 2022 23:19:46 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Linus Torvalds' <torvalds@...ux-foundation.org>
CC:     James Bottomley <James.Bottomley@...senpartnership.com>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        KVM list <kvm@...r.kernel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>,
        "linux1394-devel@...ts.sourceforge.net" 
        <linux1394-devel@...ts.sourceforge.net>,
        "drbd-dev@...ts.linbit.com" <drbd-dev@...ts.linbit.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        CIFS <linux-cifs@...r.kernel.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        linux-scsi <linux-scsi@...r.kernel.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "kgdb-bugreport@...ts.sourceforge.net" 
        <kgdb-bugreport@...ts.sourceforge.net>,
        "bcm-kernel-feedback-list@...adcom.com" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        "Arnd Bergman" <arnd@...db.de>,
        Linux PM <linux-pm@...r.kernel.org>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        dma <dmaengine@...r.kernel.org>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Jakob Koschel <jakobkoschel@...il.com>,
        "v9fs-developer@...ts.sourceforge.net" 
        <v9fs-developer@...ts.sourceforge.net>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "samba-technical@...ts.samba.org" <samba-technical@...ts.samba.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux F2FS Dev Mailing List 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "tipc-discussion@...ts.sourceforge.net" 
        <tipc-discussion@...ts.sourceforge.net>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Christian König <christian.koenig@....com>,
        "Mike Rapoport" <rppt@...nel.org>
Subject: RE: [PATCH 2/6] treewide: remove using list iterator after loop body
 as a ptr

From: Linus Torvalds
> Sent: 01 March 2022 23:03
> 
> On Tue, Mar 1, 2022 at 2:58 PM David Laight <David.Laight@...lab.com> wrote:
> >
> > Can it be resolved by making:
> > #define list_entry_is_head(pos, head, member) ((pos) == NULL)
> > and double-checking that it isn't used anywhere else (except in
> > the list macros themselves).
> 
> Well, yes, except for the fact that then the name is entirely misleading...
> 
> And somebody possibly uses it together with list_first_entry() etc, so
> it really is completely broken to mix that change with the list
> traversal change.

Probably true :-(

Actually adding list_entry_not_found() as a synonym for
list_entry_is_head() and changing the 25ish places that
use it after a loop might work.

Once that is done the loop can be changed at the same time
as list_entry_not_found().
That won't affect the in-tree callers.
(and my out of tree modules don't use those lists - so I
don't care about that!)

Having said that there are so few users of list_entry_is_head()
it is reasonable to generate two new names.
One for use after list_for_each_entry() and one for list_next_entry().
Then the change all the call sites.
After that list_entry_is_head() can be deleted - breaking out of
tree compiles.
Finally list_for_each_entry() can be rewritten to set NULL
at the end of the list.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)