linux-kernel - [PATCH 4.19 174/361] Smack: ptrace capability use fixes

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Date:   Sun, 11 Nov 2018 14:18:41 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Casey Schaufler <casey@...aufler-ca.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 174/361] Smack: ptrace capability use fixes

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 security/smack/smack_lsm.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -421,6 +421,7 @@ static int smk_ptrace_rule_check(struct
 	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);
@@ -429,7 +430,8 @@ static int smk_ptrace_rule_check(struct
 	}
 
 	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) &&
@@ -439,7 +441,7 @@ static int smk_ptrace_rule_check(struct
 			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;
@@ -1841,6 +1843,7 @@ static int smack_file_send_sigiotask(str
 {
 	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;
@@ -1854,8 +1857,12 @@ static int smack_file_send_sigiotask(str
 	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);