linux-kernel - [PATCH AUTOSEL 4.18 113/126] Smack: ptrace capability use fixes

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Message-Id: <20181031230754.29029-113-sashal@kernel.org>
Date:   Wed, 31 Oct 2018 19:07:41 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Casey Schaufler <casey.schaufler@...el.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.18 113/126] Smack: ptrace capability use fixes

From: Casey Schaufler <casey.schaufler@...el.com>

[ Upstream commit dcb569cf6ac99ca899b8109c128b6ae52477a015 ]

This fixes a pair of problems in the Smack ptrace checks
related to checking capabilities. In both cases, as reported
by Lukasz Pawelczyk, the raw capability calls are used rather
than the Smack wrapper that check addition restrictions.
In one case, as reported by Jann Horn, the wrong task is being
checked for capabilities.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 security/smack/smack_lsm.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 8b6cd5a79bfa..a81d815c81f3 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -420,6 +420,7 @@ static int smk_ptrace_rule_check(struct task_struct *tracer,
 	struct smk_audit_info ad, *saip = NULL;
 	struct task_smack *tsp;
 	struct smack_known *tracer_known;
+	const struct cred *tracercred;
 
 	if ((mode & PTRACE_MODE_NOAUDIT) == 0) {
 		smk_ad_init(&ad, func, LSM_AUDIT_DATA_TASK);
@@ -428,7 +429,8 @@ static int smk_ptrace_rule_check(struct task_struct *tracer,
 	}
 
 	rcu_read_lock();
-	tsp = __task_cred(tracer)->security;
+	tracercred = __task_cred(tracer);
+	tsp = tracercred->security;
 	tracer_known = smk_of_task(tsp);
 
 	if ((mode & PTRACE_MODE_ATTACH) &&
@@ -438,7 +440,7 @@ static int smk_ptrace_rule_check(struct task_struct *tracer,
 			rc = 0;
 		else if (smack_ptrace_rule == SMACK_PTRACE_DRACONIAN)
 			rc = -EACCES;
-		else if (capable(CAP_SYS_PTRACE))
+		else if (smack_privileged_cred(CAP_SYS_PTRACE, tracercred))
 			rc = 0;
 		else
 			rc = -EACCES;
@@ -1840,6 +1842,7 @@ static int smack_file_send_sigiotask(struct task_struct *tsk,
 {
 	struct smack_known *skp;
 	struct smack_known *tkp = smk_of_task(tsk->cred->security);
+	const struct cred *tcred;
 	struct file *file;
 	int rc;
 	struct smk_audit_info ad;
@@ -1853,8 +1856,12 @@ static int smack_file_send_sigiotask(struct task_struct *tsk,
 	skp = file->f_security;
 	rc = smk_access(skp, tkp, MAY_DELIVER, NULL);
 	rc = smk_bu_note("sigiotask", skp, tkp, MAY_DELIVER, rc);
-	if (rc != 0 && has_capability(tsk, CAP_MAC_OVERRIDE))
+
+	rcu_read_lock();
+	tcred = __task_cred(tsk);
+	if (rc != 0 && smack_privileged_cred(CAP_MAC_OVERRIDE, tcred))
 		rc = 0;
+	rcu_read_unlock();
 
 	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
 	smk_ad_setfield_u_tsk(&ad, tsk);
-- 
2.17.1