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ext4: prevent creating duplicate encrypted filenames

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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: 4461471107b7 ("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>
This commit is contained in:
Eric Biggers 2020-12-28 10:54:31 -08:00 committed by Greg Kroah-Hartman
parent faa72d97c3
commit 3ebfed353a
1 changed files with 3 additions and 0 deletions
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3
fs/ext4/namei.c
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@ -2192,6 +2192,9 @@ 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 (ext4_has_strict_mode(sbi) && IS_CASEFOLDED(dir) &&
sbi->s_encoding && utf8_validate(sbi->s_encoding, &dentry->d_name))