bug in kernel

bug in kernel

[Evgeniy]

Here is a simple program.

#include <stdio.h>
#include <errno.h>
main(){
  int err;
  err=read(0,NULL,6);
  printf("%d %d\n",err,errno);
}

I think that it should be an error : Null pointer assignment, like in windows.
But in practise it is not so. 
Mandrake Linux kernel 2.4.21-0.13mdk
I am a programmer too and i am very interested to solve this problem. Please, 
send me fragment of sourse code of kernel with this bug.
Thanks.
Sorry for my English

Re: bug in kernel

[Arjan van de Ven]

On Mon, 2005-03-14 at 17:48 +0300, Evgeniy wrote:
> Here is a simple program.
> 
> #include <stdio.h>
> #include <errno.h>
> main(){
>   int err;
>   err=read(0,NULL,6);
>   printf("%d %d\n",err,errno);
> }
> 
> I think that it should be an error : Null pointer assignment, like in windows.
> But in practise it is not so. 
> Mandrake Linux kernel 2.4.21-0.13mdk
> I am a programmer too and i am very interested to solve this problem. Please, 
> send me fragment of sourse code of kernel with this bug.

well what is the value of errno ?
-EFAULT by chance ?

Re: bug in kernel

[Arjan van de Ven]

On Mon, 2005-03-14 at 15:51 +0100, Arjan van de Ven wrote:
> On Mon, 2005-03-14 at 17:48 +0300, Evgeniy wrote:
> > Here is a simple program.
> > 
> > #include <stdio.h>
> > #include <errno.h>
> > main(){
> >   int err;
> >   err=read(0,NULL,6);
> >   printf("%d %d\n",err,errno);
> > }
> > 
> > I think that it should be an error : Null pointer assignment, like in windows.
> > But in practise it is not so. 
> > Mandrake Linux kernel 2.4.21-0.13mdk
> > I am a programmer too and i am very interested to solve this problem. Please, 
> > send me fragment of sourse code of kernel with this bug.
> 
> well what is the value of errno ?
> -EFAULT by chance ?

note that you need to include <unistd.h> for the proper read() prototype
btw

Re: bug in kernel

[Bernhard Rosenkraenzer]

On Monday 14 March 2005 15:48, Evgeniy wrote:
> #include <stdio.h>
> #include <errno.h>
> main(){
>   int err;
>   err=read(0,NULL,6);
>   printf("%d %d\n",err,errno);
> }

On my box (2.6.11), that does exactly what it is supposed to do -- "-1 14"
14 == EFAULT == "Bad Address", which is what NULL is...

Btw, printf("%d %d %s\n", err, errno, strerror(errno)); gives you a more 
readable error, that would immediately show you did get the right error.

Re: bug in kernel

[Pat Kane]

I ran the little test program on my 2.4.26  Knoppix system, and got the 
following two results:

  strace a.out < /dev/tty
   ...
   read(0, NULL, 6)                        = 1
   ...

  strace a.out < /dev/zero
   ...
   read(0, 0, 6)                           = -1 EFAULT (Bad address)
   ...

The first case looks broken.

Pat
---

Re: bug in kernel

[Martin Zwickel]

[-- Attachment #1: Type: text/plain, Size: 633 bytes --]

On Mon, 14 Mar 2005 17:48:05 +0300
Evgeniy <shubin_evgeniy@mail.ru> bubbled:

> Here is a simple program.
> 
> #include <stdio.h>
> #include <errno.h>
> main(){
>   int err;
>   err=read(0,NULL,6);
>   printf("%d %d\n",err,errno);
> }

Results:
# ./a < /dev/zero 
read(0, 0, 6)                           = -1 EFAULT (Bad address)
-1 14 Bad address

So everything is fine...

Regards,
Martin

-- 
MyExcuse:
I'd love to help you -- it's just that the Boss won't let me near the
computer.

Martin Zwickel <martin.zwickel@technotrend.de>
Research & Development

TechnoTrend AG <http://www.technotrend.de>

[-- Attachment #2: Type: application/pgp-signature, Size: 189 bytes --]

Re: bug in kernel

[linux-os]

On Mon, 14 Mar 2005, Evgeniy wrote:

> Here is a simple program.
>
> #include <stdio.h>
> #include <errno.h>
> main(){
>  int err;
>  err=read(0,NULL,6);
>  printf("%d %d\n",err,errno);
> }
>
> I think that it should be an error : Null pointer assignment, like in windows.
> But in practise it is not so.

It is an error. It will wait <forever> until you enter the [Enter]
key (it's reading from STDIN_FILENO). Then it will return -1 which
means there was an error, the error code in errno is 14 (EFAULT)
or "bad address".

You can configure user-mode code to "seg-fault" upon receiving
such an error. It can print a nasty message and leave a worthless
core file in your directory.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
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