From: Eric Biggers ebiggers@google.com

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: 4461471107b7 ("ext4 crypto: enable filename encryption") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers ebiggers@google.com --- fs/ext4/namei.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 33509266f5a0..793fc7db9d28 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -2195,6 +2195,9 @@ 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; + #ifdef CONFIG_UNICODE if (sb_has_strict_encoding(sb) && IS_CASEFOLDED(dir) && sb->s_encoding && utf8_validate(sb->s_encoding, &dentry->d_name))