From: Christopher Hodgkins <George.Hodgkins@colorado.edu>
To: musl@lists.openwall.com
Subject: [musl] Failing assertions in get_meta
Date: Tue, 20 Jul 2021 13:19:58 -0600 [thread overview]
Message-ID: <CAGd_VJy7DCcG+RN-yAeZzNcChZ7AJnjKNLm+AXT-wNT56=21Yw@mail.gmail.com> (raw)
[-- Attachment #1: Type: text/plain, Size: 1666 bytes --]
Hi all,
I'm working on a modified version of musl for some research.
We replaced the typical memory provisioning methods (mmap/brk)
with our own versions which change the backing of the provided memory,
but maintain the same semantics from the perspective of the caller,
except that the program break is no longer adjacent to the rest of the
mapped binary.
We have been encountering various failed assertions in mallocng during
debugging
in the get_meta function. Specifically, we see the assertion at line 141 in
meta.h (meta == mem->base)
failing when free()-ing memory previously allocated with malloc(),
and the assertion at line 131 ( !((uintptr_t)p & 15) ) failing for calls to
posix_memalign
with an alignment of 16 and a length of 704. Could our changes in the
backing of provisioned memory cause this?
Related question: We are aware of (and have disabled) the "donation"
functionality in the loader.
Are there other out-of-band (i.e. not mmap/sbrk) sources of memory used by
mallocng?
The errors are caused in some way by our changes, but we haven't changed
anything inside the allocator,
except to point the brk() macro to our own implementation rather than the
syscall.
So I assume there must be either some memory getting used that we don't
know about,
or some error in our implementation.
Thanks for your assistance,
George
Build info:
Working from commit 1f0c7cb1cc2170bf230623dc0b57d9a9f001af08 on master
(HEAD at time of writing).
Installed at /usr in a Docker container running Alpine Linux 3.14 on x86_64.
Musl was compiled with --enable-debug and -O0. Our test programs are
compiled with normal gcc inside the
container after installing musl.
[-- Attachment #2: Type: text/html, Size: 2008 bytes --]
next reply other threads:[~2021-07-20 19:22 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-20 19:19 Christopher Hodgkins [this message]
2021-07-20 23:40 ` Rich Felker
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='CAGd_VJy7DCcG+RN-yAeZzNcChZ7AJnjKNLm+AXT-wNT56=21Yw@mail.gmail.com' \
--to=george.hodgkins@colorado.edu \
--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).