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DescriptionCarlos O'Donell
2019-02-25 22:35:15 UTC
When dlopening a shared object, _dl_open_check will throw an exception
if CET shadow stack is enabled and the shared object has no shadow stack
support. dl_open_worker must call _dl_open_check after relocation is
finished. Otherwise, the dependency shared objects may be mmapped
without relocation. This will lead to run-time failure later when they
are needed by another dlopened shared object which is shadow stack
enabled.
https://sourceware.org/ml/libc-alpha/2019-02/msg00579.htmlhttps://sourceware.org/bugzilla/show_bug.cgi?id=24259
Note: My understanding is that this bug is visible even on non-CET hardware because the CET markup is checked for consistency even in non-CET mode, which makes this bug visible on current x86 hardware.
Commit:
commit d0093c5cefb7f7a4143f3bb03743633823229cc6
Author: H.J. Lu <hjl.tools>
Date: Mon Jul 1 12:23:10 2019 -0700
Call _dl_open_check after relocation [BZ #24259]
This is a workaround for [BZ #20839] which doesn't remove the NODELETE
object when _dl_open_check throws an exception. Move it after relocation
in dl_open_worker to avoid leaving the NODELETE object mapped without
relocation.
Please also verify upstream branch backports:
release/2.30/master - May be required. Please check.
release/2.29/master - May be required. Please check.
release/2.28/master - May be required. Please check.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2020:1828