* Question about output of kmalloc()
@ 2020-01-14 7:20 xuesong Chen
2020-01-14 10:36 ` David Laight
0 siblings, 1 reply; 3+ messages in thread
From: xuesong Chen @ 2020-01-14 7:20 UTC (permalink / raw)
To: linux-kernel; +Cc: xuesong Chen
Hello,
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?
^ permalink raw reply [flat|nested] 3+ messages in thread* RE: Question about output of kmalloc()
2020-01-14 7:20 Question about output of kmalloc() xuesong Chen
@ 2020-01-14 10:36 ` David Laight
2020-01-14 11:50 ` xuesong Chen
0 siblings, 1 reply; 3+ messages in thread
From: David Laight @ 2020-01-14 10:36 UTC (permalink / raw)
To: 'xuesong Chen', linux-kernel
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.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: Question about output of kmalloc()
2020-01-14 10:36 ` David Laight
@ 2020-01-14 11:50 ` xuesong Chen
0 siblings, 0 replies; 3+ messages in thread
From: xuesong Chen @ 2020-01-14 11:50 UTC (permalink / raw)
To: David Laight; +Cc: linux-kernel
On Tue, Jan 14, 2020 at 6:36 PM David Laight <David.Laight@aculab.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
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-01-14 7:20 Question about output of kmalloc() xuesong Chen
2020-01-14 10:36 ` David Laight
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