linux-kernel - [PATCH 5.10 524/663] selinux: fix inconsistency between inode_getxattr and inode

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Message-Id: <20210301161207.767857253@linuxfoundation.org>
Date:   Mon,  1 Mar 2021 17:12:52 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Michael Labriola <michael.d.labriola@...il.com>,
        Amir Goldstein <amir73il@...il.com>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Paul Moore <paul@...l-moore.com>
Subject: [PATCH 5.10 524/663] selinux: fix inconsistency between inode_getxattr and inode_listsecurity

From: Amir Goldstein <amir73il@...il.com>

commit a9ffe682c58aaff643764547f5420e978b6e0830 upstream.

When inode has no listxattr op of its own (e.g. squashfs) vfs_listxattr
calls the LSM inode_listsecurity hooks to list the xattrs that LSMs will
intercept in inode_getxattr hooks.

When selinux LSM is installed but not initialized, it will list the
security.selinux xattr in inode_listsecurity, but will not intercept it
in inode_getxattr.  This results in -ENODATA for a getxattr call for an
xattr returned by listxattr.

This situation was manifested as overlayfs failure to copy up lower
files from squashfs when selinux is built-in but not initialized,
because ovl_copy_xattr() iterates the lower inode xattrs by
vfs_listxattr() and vfs_getxattr().

Match the logic of inode_listsecurity to that of inode_getxattr and
do not list the security.selinux xattr if selinux is not initialized.

Reported-by: Michael Labriola <michael.d.labriola@...il.com>
Tested-by: Michael Labriola <michael.d.labriola@...il.com>
Link: https://lore.kernel.org/linux-unionfs/2nv9d47zt7.fsf@aldarion.sourceruckus.org/
Fixes: c8e222616c7e ("selinux: allow reading labels before policy is loaded")
Cc: stable@...r.kernel.org#v5.9+
Signed-off-by: Amir Goldstein <amir73il@...il.com>
Reviewed-by: Ondrej Mosnacek <omosnace@...hat.com>
Signed-off-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 security/selinux/hooks.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3414,6 +3414,10 @@ static int selinux_inode_setsecurity(str
 static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size)
 {
 	const int len = sizeof(XATTR_NAME_SELINUX);
+
+	if (!selinux_initialized(&selinux_state))
+		return 0;
+
 	if (buffer && len <= buffer_size)
 		memcpy(buffer, XATTR_NAME_SELINUX, len);
 	return len;