To: Kees Cook <keescook@chromium.org>, David Howells <dhowells@redhat.com>,
        Serge Hallyn <serge@hallyn.com>,
        James Morris <james.l.morris@oracle.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        regressions@leemhuis.info, Martin Pitt <mpitt@redhat.com>
From: Laura Abbott <labbott@redhat.com>
Subject: Coredump regression with e37fdb785a5f ("exec: Use secureexec for
 setting dumpability")
Message-ID: <87300dbc-6c72-7b2e-f5e3-3b33a811fcfa@redhat.com>
Date: Mon, 18 Dec 2017 15:17:32 -0800
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Hi,

Fedora got a bug report https://bugzilla.redhat.com/show_bug.cgi?id=1525974
of coredumps failing for systemd units. If systemd units segfault, no
core is produced.

commit e37fdb785a5f95ecadf43b773c97f676500ac7b8 (refs/bisect/bad)
Author: Kees Cook <keescook@chromium.org>
Date:   Tue Jul 18 15:25:31 2017 -0700

     exec: Use secureexec for setting dumpability
     
     The examination of "current" to decide dumpability is wrong. This was a
     check of and euid/uid (or egid/gid) mismatch in the existing process,
     not the newly created one. This appears to stretch back into even the
     "history.git" tree. Luckily, dumpability is later set in commit_creds().
     In earlier kernel versions before creds existed, similar checks also
     existed late in the exec flow, covering up the mistake as far back as I
     could find.
     
     Note that because the commit_creds() check examines differences of euid,
     uid, egid, gid, and capabilities between the old and new creds, it would
     look like the setup_new_exec() dumpability test could be entirely removed.
     However, the secureexec test may cover a different set of tests (specific
     to the LSMs) than what commit_creds() checks for. So, fix this test to
     use secureexec (the removed euid tests are redundant to the commoncap
     secureexec checks now).
     
     Cc: David Howells <dhowells@redhat.com>
     Signed-off-by: Kees Cook <keescook@chromium.org>
     Acked-by: Serge Hallyn <serge@hallyn.com>
     Reviewed-by: James Morris <james.l.morris@oracle.com>


This was still broken as of -rc3 although interestingly enough this worked
on my rawhide system. Any ideas?

Thanks,
Laura