linux-kernel - Re: Really good idea to allow mmap(0, FIXED)?

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]

Date:	Fri, 06 Oct 2006 09:25:15 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	David Wagner <daw-usenet@...erner.cs.berkeley.edu>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Really good idea to allow mmap(0, FIXED)?

On Thu, 2006-10-05 at 23:55 +0000, David Wagner wrote:
> Michael Buesch  wrote:
> >Is is really a good idea to allow processes to remap something
> >to address 0?
> >I say no, because this can potentially be used to turn rather harmless
> >kernel bugs into a security vulnerability.
> 
> Let me see if I understand.  If the kernel does this somewhere:
> 
>     struct s *foo;
>     foo->x->y = 0;
> 
> and if there is some way that userland code can cause this to be
> executed with 'foo' set to a NULL pointer, then user-land code can
> do this:
> 
>     mmap(0, 4096, PROT_READ|PROT_EXEC|PROT_WRITE,
>         MAP_FIXED|MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
>     struct s *bar = 0;

the question isn't if it's a good idea to allow mmap(0) but to allow
mmap PROT_WRITE | PROT_EXEC !


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/