From: keescook@chromium.org (Kees Cook)
To: linux-security-module@vger.kernel.org
Subject: [PATCH v2 3/8] exec: Use secureexec for setting dumpability
Date: Mon, 10 Jul 2017 00:57:26 -0700 [thread overview]
Message-ID: <1499673451-66160-4-git-send-email-keescook@chromium.org> (raw)
In-Reply-To: <1499673451-66160-1-git-send-email-keescook@chromium.org>
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.
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, but
strictly speaking, the secureexec test covers a different set of tests
than what commit_creds() checks for. So, fix this test to use secureexec,
which includes the same logical check (euid != uid || egid != gid),
but checks bprm->cred, not current->cred.
One would wonder if we need a security_commit_creds() LSM hook and to
move the existing checks in commit_creds() into commoncaps.c, which
would allow expanding the logic to all LSMs. Currently this doesn't
seem needed, though.
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/exec.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/exec.c b/fs/exec.c
index b92e37fb53aa..3e519d4f0bd3 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1346,7 +1346,7 @@ void setup_new_exec(struct linux_binprm * bprm)
current->sas_ss_sp = current->sas_ss_size = 0;
- if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
+ if (!bprm->secureexec)
set_dumpable(current->mm, SUID_DUMP_USER);
else
set_dumpable(current->mm, suid_dumpable);
--
2.7.4
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next prev parent reply other threads:[~2017-07-10 7:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-10 7:57 [PATCH v2 0/8] exec: Use sane stack rlimit under secureexec Kees Cook
2017-07-10 7:57 ` [PATCH v2 1/8] exec: Correct comments about "point of no return" Kees Cook
2017-07-10 8:46 ` Eric W. Biederman
2017-07-10 16:04 ` Kees Cook
[not found] ` <87pod8mdad.fsf@xmission.com>
2017-07-18 6:39 ` Kees Cook
2017-07-18 13:12 ` Eric W. Biederman
2017-07-18 13:42 ` Kees Cook
2017-07-10 7:57 ` [PATCH v2 2/8] exec: Move security_bprm_secureexec() earlier Kees Cook
2017-07-10 8:57 ` Eric W. Biederman
2017-07-10 16:06 ` Kees Cook
[not found] ` <87bmosmcqv.fsf@xmission.com>
2017-07-11 2:07 ` Kees Cook
2017-07-18 6:45 ` Kees Cook
2017-07-10 7:57 ` Kees Cook [this message]
2017-07-10 7:57 ` [PATCH v2 4/8] exec: Use secureexec for clearing pdeath_signal Kees Cook
2017-07-10 7:57 ` [PATCH v2 5/8] smack: Remove redundant pdeath_signal clearing Kees Cook
2017-07-10 7:57 ` [PATCH v2 6/8] exec: Consolidate dumpability logic Kees Cook
2017-07-10 7:57 ` [PATCH v2 7/8] exec: Consolidate pdeath_signal clearing Kees Cook
2017-07-10 7:57 ` [PATCH v2 8/8] exec: Use sane stack rlimit under secureexec Kees Cook
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