| Message ID | 20210527235236.2376556-1-ebiggers@kernel.org (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | fscrypt: don't ignore minor_hash when hash is 0 | expand |
On Thu, May 27, 2021 at 04:52:36PM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@google.com> > > When initializing a no-key name, fscrypt_fname_disk_to_usr() sets the > minor_hash to 0 if the (major) hash is 0. > > This doesn't make sense because 0 is a valid hash code, so we shouldn't > ignore the filesystem-provided minor_hash in that case. Fix this by > removing the special case for 'hash == 0'. > > This is an old bug that appears to have originated when the encryption > code in ext4 and f2fs was moved into fs/crypto/. The original ext4 and > f2fs code passed the hash by pointer instead of by value. So > 'if (hash)' actually made sense then, as it was checking whether a > pointer was NULL. But now the hashes are passed by value, and > filesystems just pass 0 for any hashes they don't have. There is no > need to handle this any differently from the hashes actually being 0. > > It is difficult to reproduce this bug, as it only made a difference in > the case where a filename's 32-bit major hash happened to be 0. > However, it probably had the largest chance of causing problems on > ubifs, since ubifs uses minor_hash to do lookups of no-key names, in > addition to using it as a readdir cookie. ext4 only uses minor_hash as > a readdir cookie, and f2fs doesn't use minor_hash at all. > > Fixes: 0b81d0779072 ("fs crypto: move per-file encryption from f2fs tree to fs/crypto") > Cc: <stable@vger.kernel.org> # v4.6+ > Signed-off-by: Eric Biggers <ebiggers@google.com> > --- > fs/crypto/fname.c | 10 +++------- > 1 file changed, 3 insertions(+), 7 deletions(-) > Applied to fscrypt.git#master for 5.14. - Eric
diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c index 6ca7d16593ff..d00455440d08 100644 --- a/fs/crypto/fname.c +++ b/fs/crypto/fname.c @@ -344,13 +344,9 @@ int fscrypt_fname_disk_to_usr(const struct inode *inode, offsetof(struct fscrypt_nokey_name, sha256)); BUILD_BUG_ON(BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX) > NAME_MAX); - if (hash) { - nokey_name.dirhash[0] = hash; - nokey_name.dirhash[1] = minor_hash; - } else { - nokey_name.dirhash[0] = 0; - nokey_name.dirhash[1] = 0; - } + nokey_name.dirhash[0] = hash; + nokey_name.dirhash[1] = minor_hash; + if (iname->len <= sizeof(nokey_name.bytes)) { memcpy(nokey_name.bytes, iname->name, iname->len); size = offsetof(struct fscrypt_nokey_name, bytes[iname->len]);