Commit abd561e5 authored Dec 28, 2020 by Eric Biggers Committed by Greg Kroah-Hartman Jan 06, 2021

ext4: prevent creating duplicate encrypted filenames

commit 75d18cd1868c2aee43553723872c35d7908f240f upstream.

As described in "fscrypt: add fscrypt_is_nokey_name()", it's possible to
create a duplicate filename in an encrypted directory by creating a file
concurrently with adding the directory's encryption key.

Fix this bug on ext4 by rejecting no-key dentries in ext4_add_entry().

Note that the duplicate check in ext4_find_dest_de() sometimes prevented
this bug.  However in many cases it didn't, since ext4_find_dest_de()
doesn't examine every dentry.

Fixes: 44614711 ("ext4 crypto: enable filename encryption")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20201118075609.120337-3-ebiggers@kernel.org


Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 1227ffc9

fs/ext4/namei.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2106,6 +2106,9 @@ static int ext4_add_entry(handle_t handle, struct dentry dentry,
		if (!dentry->d_name.len)
		return -EINVAL;

		if (fscrypt_is_nokey_name(dentry))
		return -ENOKEY;

		retval = ext4_fname_setup_filename(dir, &dentry->d_name, 0, &fname);
		if (retval)
		return retval;