linux-kernel - Re: Question about output of kmalloc()

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Message-ID: <CAJKSTDxsSH=ToKhhBizydi6KiJkSxhAcKAHOo1593p3L3At0Zg@mail.gmail.com>
Date:   Tue, 14 Jan 2020 19:50:13 +0800
From:   xuesong Chen <xuesong1977@...il.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Question about output of kmalloc()

On Tue, Jan 14, 2020 at 6:36 PM David Laight <David.Laight@...lab.com> wrote:
>
> From:  xuesong Chen
> > Sent: 14 January 2020 07:21
> > Below code snippet in the .ko:
> >
> > unsigned long *p = (unsigned long *)kmalloc(sizeof(*p), GFP_KERNEL);
> > printk("Addr of p = 0x%p\n", p);
> >
> > The output is:
> > Addr of p = 0x0000000018606ce7
> >
> > In my mind, during the early day, the p should be 0xfffff...., can
> > anybody give some tips why the output looks like it's a physical
> > address?
>
> The printed value is hashed to avoid leaking info.
>
But '%px' can print the correct value, so seems the infoleak is still
there... BTW, kindly point me to the hashed address code part?
>
>
>         David
>
> -
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