From: Rich Felker <dalias@aerifal.cx>
To: musl@lists.openwall.com
Subject: Re: malloc and linux memory layout
Date: Thu, 11 Aug 2011 10:54:58 -0400 [thread overview]
Message-ID: <20110811145458.GE132@brightrain.aerifal.cx> (raw)
In-Reply-To: <20110811074305.GA4276@albatros>
On Thu, Aug 11, 2011 at 11:43:05AM +0400, Vasiliy Kulikov wrote:
> > The mmap zone (where mmaps are put by
> > default) starts just below the stack limit and continues downward as
> > more mappings are made.
>
> Not only this zone. mmap() can return address before main program text if
> there is enough space there.
Interesting.
> Other minor (Linux-specific) things:
>
> Low unmappable pages region might be absent if the task has CAP_SYS_RAWIO
> capability. But pages before mmap_min_addr will be mmap'ed only by
> explicit mmap(addr, ..., MAP_FIXED, ...), no libs will be there.
This is mostly irrelevant since it requires root or equivalent.
(CAP_SYS_RAWIO might as well be root since it lets you exploit
kernelspace null pointer dereference bugs to get root).
> "Reserved for kernelspace use" region might be absent too for 32-bit
> tasks running on 286-64 system.
Nice.
Rich
prev parent reply other threads:[~2011-08-11 14:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-10 19:56 Rich Felker
2011-08-11 7:43 ` Vasiliy Kulikov
2011-08-11 14:54 ` Rich Felker [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110811145458.GE132@brightrain.aerifal.cx \
--to=dalias@aerifal.cx \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).