linux-kernel - [PATCH] SELinux: Always allow FIOCLEX and FIONCLEX

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Date:   Tue, 25 Jan 2022 16:34:12 -0500
From:   Demi Marie Obenour <demiobenour@...il.com>
To:     Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>
Cc:     Demi Marie Obenour <demiobenour@...il.com>,
        selinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] SELinux: Always allow FIOCLEX and FIONCLEX

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.

Signed-off-by: Demi Marie Obenour <demiobenour@...il.com>
---
 security/selinux/hooks.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 5b6895e4fc29..8f3b2f15c1f3 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3728,6 +3728,11 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd,
 		error = file_has_perm(cred, file, FILE__GETATTR);
 		break;
 
+	/* must always succeed */
+	case FIOCLEX:
+	case FIONCLEX:
+		break;
+
 	case FS_IOC_SETFLAGS:
 	case FS_IOC_SETVERSION:
 		error = file_has_perm(cred, file, FILE__SETATTR);
-- 
Sincerely,
Demi Marie Obenour