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Home > Archive > Unix administration > November 2004 > What prevent a user process from writing to arbitrary memory locations
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What prevent a user process from writing to arbitrary memory locations
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| Hi All,
What prevent a user process from writing to arbitrary memory locations
Thanks
jeff
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| Michael Vilain 2004-10-27, 2:49 am |
| In article <debaf75c.0410261631.1d6cfd2e@posting.google.com>,
zhefu.fan@gmail.com (Jeff) wrote:
> What prevent a user process from writing to arbitrary memory locations
Better application coders who know what they're doing.
--
DeeDee, don't press that button! DeeDee! NO! Dee...
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| Barry Margolin 2004-10-27, 2:49 am |
| In article <debaf75c.0410261631.1d6cfd2e@posting.google.com>,
zhefu.fan@gmail.com (Jeff) wrote:
> Hi All,
>
> What prevent a user process from writing to arbitrary memory locations
Addresses used by user processes are virtual addresses, not physical
addresses. The VM mechanism translates these to physical addresses, and
this mechanism only recognizes addresses that are within the process's
address space. On some systems kernel memory is also mapped into the
process's memory, but VM also supports page-level protection, so the
pages that refer to kernel memory have restrictive access.
--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
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| phn@icke-reklam.ipsec.nu 2004-10-27, 2:49 am |
| Jeff <zhefu.fan@gmail.com> wrote:
> Hi All,
> What prevent a user process from writing to arbitrary memory locations
An operating system combined with MMU hardware.
Somer OS-es does a bad job in this area, allowing sleezze-ware to propagate.
> Thanks
> jeff
--
Peter Håkanson
IPSec Sverige ( At Gothenburg Riverside )
Sorry about my e-mail address, but i'm trying to keep spam out,
remove "icke-reklam" if you feel for mailing me. Thanx.
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| Michael Paoli 2004-10-27, 5:52 pm |
| UNIX is a multi-user multi-tasking operating system. In such a system,
part of the basic security necessary for a reasonably secure system
includes not allowing arbitrary (e.g. user) processes to access
arbitrary memory locations. Such basic fundamental memory management
is a core part of the UNIX opreating system. Depending on hardware, this
may be assisted and/or significantly enforced as part of hardware
memory management.
zhefu.fan@gmail.com (Jeff) wrote in message news:<debaf75c.0410261631.1d6cfd2e@posting.google.com>...
> What prevent a user process from writing to arbitrary memory locations
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| Kevin Collins 2004-11-03, 5:53 pm |
| In article <debaf75c.0410261631.1d6cfd2e@posting.google.com>, Jeff wrote:
> Hi All,
>
> What prevent a user process from writing to arbitrary memory locations
>
>
> Thanks
>
> jeff
Jeff - could you please use a "brief" Subject line and not ask your entire
question there? Its a little frustrating to see a 70 character subject, or even
longer (as in your following post). In my newsreader (slrn), I have to scroll
to the right just to see your subject...
Thanks,
Kevin
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| Bill Marcum 2004-11-04, 7:48 am |
| On Wed, 03 Nov 2004 20:03:13 GMT, Kevin Collins
<spamtotrash@toomuchfiction.com> wrote:
>
> Jeff - could you please use a "brief" Subject line and not ask your entire
> question there? Its a little frustrating to see a 70 character subject, or even
> longer (as in your following post). In my newsreader (slrn), I have to scroll
> to the right just to see your subject...
>
In slrn you can press w to wrap long lines in the subject or body. You
do have to scroll if you want to see the subject before reading the
message.
--
Of course power tools and alcohol don't mix. Everyone knows power
tools aren't soluble in alcohol...
-- Crazy Nigel
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| Kevin Collins 2004-11-04, 5:50 pm |
| In article <3p6p52-jvs.ln1@don.localnet>, Bill Marcum wrote:
> On Wed, 03 Nov 2004 20:03:13 GMT, Kevin Collins
> <spamtotrash@toomuchfiction.com> wrote:
> In slrn you can press w to wrap long lines in the subject or body. You
> do have to scroll if you want to see the subject before reading the
> message.
Thanks for that tip...
Kevin
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