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Date: Thu, 6 Oct 2022 01:27:35 -0700
From: Kees Cook <keescook@...omium.org>
To: Eric Biederman <ebiederm@...ssion.com>
Cc: Kees Cook <keescook@...omium.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
John Johansen <john.johansen@...onical.com>,
Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Stephen Smalley <stephen.smalley.work@...il.com>,
Eric Paris <eparis@...isplace.org>,
Richard Haines <richard_c_haines@...nternet.com>,
Casey Schaufler <casey@...aufler-ca.com>,
Xin Long <lucien.xin@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Todd Kjos <tkjos@...gle.com>,
Ondrej Mosnacek <omosnace@...hat.com>,
linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
apparmor@...ts.ubuntu.com, linux-security-module@...r.kernel.org,
selinux@...r.kernel.org,
Jorge Merlino <jorge.merlino@...onical.com>,
"Christian Brauner (Microsoft)" <brauner@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Andy Lutomirski <luto@...nel.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Prashanth Prahlad <pprahlad@...hat.com>,
Micah Morton <mortonm@...omium.org>,
Fenghua Yu <fenghua.yu@...el.com>,
Andrei Vagin <avagin@...il.com>, linux-kernel@...r.kernel.org,
linux-hardening@...r.kernel.org
Subject: [PATCH 2/2] exec: Remove LSM_UNSAFE_SHARE
With fs_struct explicitly unshared during exec, it is no longer possible
to have unexpected shared state, and LSM_UNSAFE_SHARE can be entirely
removed.
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Eric Biederman <ebiederm@...ssion.com>
Cc: John Johansen <john.johansen@...onical.com>
Cc: Paul Moore <paul@...l-moore.com>
Cc: James Morris <jmorris@...ei.org>
Cc: "Serge E. Hallyn" <serge@...lyn.com>
Cc: Stephen Smalley <stephen.smalley.work@...il.com>
Cc: Eric Paris <eparis@...isplace.org>
Cc: Richard Haines <richard_c_haines@...nternet.com>
Cc: Casey Schaufler <casey@...aufler-ca.com>
Cc: Xin Long <lucien.xin@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Todd Kjos <tkjos@...gle.com>
Cc: Ondrej Mosnacek <omosnace@...hat.com>
Cc: linux-fsdevel@...r.kernel.org
Cc: linux-mm@...ck.org
Cc: apparmor@...ts.ubuntu.com
Cc: linux-security-module@...r.kernel.org
Cc: selinux@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
fs/exec.c | 17 +----------------
include/linux/security.h | 5 ++---
security/apparmor/domain.c | 5 -----
security/selinux/hooks.c | 10 ----------
4 files changed, 3 insertions(+), 34 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 7d5f63f03c58..3cd058711098 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1563,8 +1563,7 @@ EXPORT_SYMBOL(bprm_change_interp);
*/
static void check_unsafe_exec(struct linux_binprm *bprm)
{
- struct task_struct *p = current, *t;
- unsigned n_fs;
+ struct task_struct *p = current;
if (p->ptrace)
bprm->unsafe |= LSM_UNSAFE_PTRACE;
@@ -1575,20 +1574,6 @@ static void check_unsafe_exec(struct linux_binprm *bprm)
*/
if (task_no_new_privs(current))
bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
-
- t = p;
- n_fs = 1;
- spin_lock(&p->fs->lock);
- rcu_read_lock();
- while_each_thread(p, t) {
- if (t->fs == p->fs)
- n_fs++;
- }
- rcu_read_unlock();
-
- if (p->fs->users > n_fs)
- bprm->unsafe |= LSM_UNSAFE_SHARE;
- spin_unlock(&p->fs->lock);
}
static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
diff --git a/include/linux/security.h b/include/linux/security.h
index 1bc362cb413f..db508a8c3cc7 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -215,9 +215,8 @@ struct sched_param;
struct request_sock;
/* bprm->unsafe reasons */
-#define LSM_UNSAFE_SHARE 1
-#define LSM_UNSAFE_PTRACE 2
-#define LSM_UNSAFE_NO_NEW_PRIVS 4
+#define LSM_UNSAFE_PTRACE BIT(0)
+#define LSM_UNSAFE_NO_NEW_PRIVS BIT(1)
#ifdef CONFIG_MMU
extern int mmap_min_addr_handler(struct ctl_table *table, int write,
diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index 91689d34d281..1b2c0bb4d9ae 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -924,11 +924,6 @@ int apparmor_bprm_creds_for_exec(struct linux_binprm *bprm)
goto audit;
}
- if (bprm->unsafe & LSM_UNSAFE_SHARE) {
- /* FIXME: currently don't mediate shared state */
- ;
- }
-
if (bprm->unsafe & (LSM_UNSAFE_PTRACE)) {
/* TODO: test needs to be profile of label to new */
error = may_change_ptraced_domain(new, &info);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 79573504783b..3ec80cc8ad1c 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2349,16 +2349,6 @@ static int selinux_bprm_creds_for_exec(struct linux_binprm *bprm)
if (rc)
return rc;
- /* Check for shared state */
- if (bprm->unsafe & LSM_UNSAFE_SHARE) {
- rc = avc_has_perm(&selinux_state,
- old_tsec->sid, new_tsec->sid,
- SECCLASS_PROCESS, PROCESS__SHARE,
- NULL);
- if (rc)
- return -EPERM;
- }
-
/* Make sure that anyone attempting to ptrace over a task that
* changes its SID has the appropriate permit */
if (bprm->unsafe & LSM_UNSAFE_PTRACE) {
--
2.34.1
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