Bug 252549 - statically linked threaded binaries have executable thread stacks
Summary: statically linked threaded binaries have executable thread stacks
Status: In Progress
Alias: None
Product: Base System
Classification: Unclassified
Component: threads (show other bugs)
Version: CURRENT
Hardware: Any Any
: --- Affects Only Me
Assignee: freebsd-threads (Nobody)
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2021-01-10 02:49 UTC by Ed Maste
Modified: 2021-01-10 06:27 UTC (History)
1 user (show)

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Description Ed Maste freebsd_committer 2021-01-10 02:49:24 UTC 
The stack created by pthread_create in a statically linked binary has RWX protection, regardless of the binary's desired stack (via PT_GNU_STACK). Initial stack has expected protection.

See https://reviews.freebsd.org/D28050 for the discovery of this issue.

lib/libc/gen/dlfcn.c provides a weak _rtld_get_stack_prot for statically linked binaries:

#pragma weak _rtld_get_stack_prot
int
_rtld_get_stack_prot(void)
{

        return (PROT_EXEC | PROT_READ | PROT_WRITE);
}
Comment 1 Konstantin Belousov freebsd_committer 2021-01-10 03:13:04 UTC 
https://reviews.freebsd.org/D28075
Comment 2 commit-hook freebsd_committer 2021-01-10 06:27:19 UTC 
A commit in branch main references this bug:

URL: https://cgit.FreeBSD.org/src/commit/?id=81b3a0a34145ee6c855f50c8035728f76d63c3f0

commit 81b3a0a34145ee6c855f50c8035728f76d63c3f0
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2021-01-10 03:05:42 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2021-01-10 06:25:43 +0000

    libc: implement rtld_get_stack_prot() for real

    which makes stack prot correct for non-main threads created by binaries
    with statically linked libthr.

    Cache result, but do not engage into the full double-checked locking,
    since calculation of the return value is idempotent.

    PR:     252549
    Reported and reviewed by:       emaste
    MFC after:      1 week
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D28075

 lib/libc/gen/dlfcn.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)