linux-kernel - [PATCH 4.9 008/206] fscrypt: fix renaming and linking special files

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Message-Id: <20170110131503.135130403@linuxfoundation.org>
Date:   Tue, 10 Jan 2017 14:34:51 +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, Eric Biggers <ebiggers@...gle.com>,
        Richard Weinberger <richard@....at>,
        Theodore Tso <tytso@....edu>
Subject: [PATCH 4.9 008/206] fscrypt: fix renaming and linking special files

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

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

From: Eric Biggers <ebiggers@...gle.com>

commit 42d97eb0ade31e1bc537d086842f5d6e766d9d51 upstream.

Attempting to link a device node, named pipe, or socket file into an
encrypted directory through rename(2) or link(2) always failed with
EPERM.  This happened because fscrypt_has_permitted_context() saw that
the file was unencrypted and forbid creating the link.  This behavior
was unexpected because such files are never encrypted; only regular
files, directories, and symlinks can be encrypted.

To fix this, make fscrypt_has_permitted_context() always return true on
special files.

This will be covered by a test in my encryption xfstests patchset.

Fixes: 9bd8212f981e ("ext4 crypto: add encryption policy and password salt support")
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Reviewed-by: Richard Weinberger <richard@....at>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/crypto/policy.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -171,6 +171,11 @@ int fscrypt_has_permitted_context(struct
 		BUG_ON(1);
 	}

+	/* No restrictions on file types which are never encrypted */
+	if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
+	    !S_ISLNK(child->i_mode))
+		return 1;
+
 	/* no restrictions if the parent directory is not encrypted */
 	if (!parent->i_sb->s_cop->is_encrypted(parent))
 		return 1;