linux-kernel - [PATCH AUTOSEL 5.16 17/35] selinux: allow FIOCLEX and FIONCLEX with policy capability

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Message-Id: <20220328112011.1555169-17-sashal@kernel.org>
Date:   Mon, 28 Mar 2022 07:19:53 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Richard Haines <richard_c_haines@...nternet.com>,
        Demi Marie Obenour <demiobenour@...il.com>,
        Paul Moore <paul@...l-moore.com>,
        Sasha Levin <sashal@...nel.org>,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        cgzones@...glemail.com, ndesaulniers@...gle.com,
        selinux@...r.kernel.org
Subject: [PATCH AUTOSEL 5.16 17/35] selinux: allow FIOCLEX and FIONCLEX with policy capability

From: Richard Haines <richard_c_haines@...nternet.com>

[ Upstream commit 65881e1db4e948614d9eb195b8e1197339822949 ]

These ioctls are equivalent to fcntl(fd, F_SETFD, flags), which SELinux
always allows too.  Furthermore, a failed FIOCLEX could result in a file
descriptor being leaked to a process that should not have access to it.

As this patch removes access controls, a policy capability needs to be
enabled in policy to always allow these ioctls.

Based-on-patch-by: Demi Marie Obenour <demiobenour@...il.com>
Signed-off-by: Richard Haines <richard_c_haines@...nternet.com>
[PM: subject line tweak]
Signed-off-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 security/selinux/hooks.c                   | 6 ++++++
 security/selinux/include/policycap.h       | 1 +
 security/selinux/include/policycap_names.h | 3 ++-
 security/selinux/include/security.h        | 7 +++++++
 4 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index d582479dfd62..9b65ebc96b5d 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3793,6 +3793,12 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd,
 					    CAP_OPT_NONE, true);
 		break;
 
+	case FIOCLEX:
+	case FIONCLEX:
+		if (!selinux_policycap_ioctl_skip_cloexec())
+			error = ioctl_has_perm(cred, file, FILE__IOCTL, (u16) cmd);
+		break;
+
 	/* default case assumes that the command will go
 	 * to the file's ioctl() function.
 	 */
diff --git a/security/selinux/include/policycap.h b/security/selinux/include/policycap.h
index 2ec038efbb03..a9e572ca4fd9 100644
--- a/security/selinux/include/policycap.h
+++ b/security/selinux/include/policycap.h
@@ -11,6 +11,7 @@ enum {
 	POLICYDB_CAPABILITY_CGROUPSECLABEL,
 	POLICYDB_CAPABILITY_NNP_NOSUID_TRANSITION,
 	POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS,
+	POLICYDB_CAPABILITY_IOCTL_SKIP_CLOEXEC,
 	__POLICYDB_CAPABILITY_MAX
 };
 #define POLICYDB_CAPABILITY_MAX (__POLICYDB_CAPABILITY_MAX - 1)
diff --git a/security/selinux/include/policycap_names.h b/security/selinux/include/policycap_names.h
index b89289f092c9..ebd64afe1def 100644
--- a/security/selinux/include/policycap_names.h
+++ b/security/selinux/include/policycap_names.h
@@ -12,7 +12,8 @@ const char *selinux_policycap_names[__POLICYDB_CAPABILITY_MAX] = {
 	"always_check_network",
 	"cgroup_seclabel",
 	"nnp_nosuid_transition",
-	"genfs_seclabel_symlinks"
+	"genfs_seclabel_symlinks",
+	"ioctl_skip_cloexec"
 };
 
 #endif /* _SELINUX_POLICYCAP_NAMES_H_ */
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index ac0ece01305a..c0d966020ebd 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -219,6 +219,13 @@ static inline bool selinux_policycap_genfs_seclabel_symlinks(void)
 	return READ_ONCE(state->policycap[POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS]);
 }
 
+static inline bool selinux_policycap_ioctl_skip_cloexec(void)
+{
+	struct selinux_state *state = &selinux_state;
+
+	return READ_ONCE(state->policycap[POLICYDB_CAPABILITY_IOCTL_SKIP_CLOEXEC]);
+}
+
 struct selinux_policy_convert_data;
 
 struct selinux_load_state {
-- 
2.34.1