The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 75d18cd1868c2aee43553723872c35d7908f240f Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@xxxxxxxxxx>
Date: Tue, 17 Nov 2020 23:56:06 -0800
Subject: [PATCH] ext4: prevent creating duplicate encrypted filenames
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@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20201118075609.120337-3-ebiggers@xxxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
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))
