From: Alexey Izbyshev <izbyshev@ispras.ru>
To: Markus Wichmann <nullplan@gmx.net>
Cc: musl@lists.openwall.com
Subject: Re: dlsym(handle) may search in unrelated libraries
Date: Thu, 07 Feb 2019 00:23:06 +0300 [thread overview]
Message-ID: <96c367533236e3e203f04a994ee65c47@ispras.ru> (raw)
In-Reply-To: <20190206202518.GC5469@voyager>
On 2019-02-06 23:25, Markus Wichmann wrote:
> Right you are. It took me a while to understand what the deps array was
> even for (since musl's dlclose() doesn't do anything, tracking
> dependencies is mostly pointless), but I found it is needed for lazy
> relocation processing. So it is necessary for all libs opened by
> dlopen() directly to contain a list of all their dependencies. All the
> other libs can have an empty list.
Actually, dso->deps is used in dlsym(handle) because it must use the
dependency order for symbol search, so it's incorrect to have deps empty
for "all the other" libs. Consider the following modification of my
previous example:
$ cat bazdep.c
int bazdep = 1;
extern int bazdepdep;
int *p = &bazdepdep;
$ cat bazdepdep.c
int bazdepdep = 2;
$ cat main.c
#include <dlfcn.h>
#include <stdio.h>
int main(void) {
if (!dlopen("libbaz.so", RTLD_NOW|RTLD_LOCAL))
return 1;
if (!dlopen("libfoo.so", RTLD_NOW|RTLD_LOCAL))
return 1;
void *h = dlopen("libbazdep.so", RTLD_NOW|RTLD_LOCAL);
printf("%p\n", dlsym(h, "bar"));
printf("%p\n", dlsym(h, "bazdepdep"));
}
The correct output is zero in the first line and some non-zero address
in the second. Vanilla musl 1.1.21 prints two non-zero addresses. But
with your patch the output is two zeros because dlsym() can't search in
dependencies of "libbazdep.so" anymore.
Alexey
next prev parent reply other threads:[~2019-02-06 21:23 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-05 21:02 Alexey Izbyshev
2019-02-06 13:40 ` Alexey Izbyshev
2019-02-06 16:02 ` Markus Wichmann
2019-02-06 17:02 ` Alexey Izbyshev
2019-02-06 20:25 ` Markus Wichmann
2019-02-06 21:23 ` Alexey Izbyshev [this message]
2019-02-07 5:33 ` Markus Wichmann
2019-02-07 13:42 ` Alexey Izbyshev
2019-02-07 17:43 ` Markus Wichmann
2019-02-07 20:37 ` Markus Wichmann
2019-02-07 21:29 ` Rich Felker
2019-02-07 16:54 ` Rich Felker
2019-02-07 18:36 ` Markus Wichmann
2019-02-07 18:57 ` Rich Felker
2019-02-07 20:31 ` Markus Wichmann
2019-02-07 21:33 ` Rich Felker
2019-02-07 21:37 ` Rich Felker
2019-02-08 10:19 ` A. Wilcox
2019-02-08 12:00 ` Szabolcs Nagy
2019-02-08 16:09 ` Rich Felker
2019-02-09 22:53 Alexey Izbyshev
2019-02-10 1:03 ` Rich Felker
2019-02-26 15:07 ` Rich Felker
2019-03-04 2:11 ` 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=96c367533236e3e203f04a994ee65c47@ispras.ru \
--to=izbyshev@ispras.ru \
--cc=musl@lists.openwall.com \
--cc=nullplan@gmx.net \
/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).