linux-kernel - Re: [PATCH] devres: zero the memory in devm

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: <20201030105706.GK4077@smile.fi.intel.com>
Date:   Fri, 30 Oct 2020 12:57:06 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH] devres: zero the memory in devm_krealloc() if needed

On Fri, Oct 30, 2020 at 10:03:50AM +0100, Bartosz Golaszewski wrote:
> On Thu, Oct 29, 2020 at 9:05 PM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> >
> > On Mon, Oct 26, 2020 at 01:27:28PM +0100, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > >
> > > If we're returning the same pointer (when new size is smaller or equal
> > > to the old size) we need to check if the user wants the memory zeroed
> > > and memset() it manually if so.
> >
> > Any use case? Because to me it sounds contradictory to the whole idea of [k]realloc().
> 
> This is kind of a gray area in original krealloc() too and I want to
> submit a patch for mm too. Right now krealloc ignores the __GFP_ZERO
> flag if new_size <= old_size but zeroes the memory if new_size >
> old_size.

> This should be consistent - either ignore __GFP_ZERO or
> don't ignore it in both cases. I think that not ignoring it is better
> - if user passes it then it's for a reason.

Sorry, but I consider in these two choices the best is the former one, i.e.
ignoring, because non-ignoring for sizes less than current is counter the
REalloc() by definition.

Reading realloc(3):

"If the new size is larger than the old size, the added memory will not be
initialized."

So, supports my choice over yours.

-- 
With Best Regards,
Andy Shevchenko