Message ID | 20200824203841.1707847-1-ebiggers@kernel.org (mailing list archive) |
---|---|
State | Accepted |
Headers | show |
Series | fscrypt: restrict IV_INO_LBLK_32 to ino_bits <= 32 | expand |
On Mon, Aug 24, 2020 at 01:38:41PM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@google.com> > > When an encryption policy has the IV_INO_LBLK_32 flag set, the IV > generation method involves hashing the inode number. This is different > from fscrypt's other IV generation methods, where the inode number is > either not used at all or is included directly in the IVs. > > Therefore, in principle IV_INO_LBLK_32 can work with any length inode > number. However, currently fscrypt gets the inode number from > inode::i_ino, which is 'unsigned long'. So currently the implementation > limit is actually 32 bits (like IV_INO_LBLK_64), since longer inode > numbers will have been truncated by the VFS on 32-bit platforms. > > Fix fscrypt_supported_v2_policy() to enforce the correct limit. > > This doesn't actually matter currently, since only ext4 and f2fs support > IV_INO_LBLK_32, and they both only support 32-bit inode numbers. But we > might as well fix it in case it matters in the future. > > Ideally inode::i_ino would instead be made 64-bit, but for now it's not > needed. (Note, this limit does *not* prevent filesystems with 64-bit > inode numbers from adding fscrypt support, since IV_INO_LBLK_* support > is optional and is useful only on certain hardware.) > > Fixes: e3b1078bedd3 ("fscrypt: add support for IV_INO_LBLK_32 policies") > Reported-by: Jeff Layton <jlayton@kernel.org> > Signed-off-by: Eric Biggers <ebiggers@google.com> Applied to fscrypt.git#master for 5.10. - Eric
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index 2d73fd39ad96..b92f34523178 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -192,10 +192,15 @@ static bool fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 *policy, 32, 32)) return false; + /* + * IV_INO_LBLK_32 hashes the inode number, so in principle it can + * support any ino_bits. However, currently the inode number is gotten + * from inode::i_ino which is 'unsigned long'. So for now the + * implementation limit is 32 bits. + */ if ((policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) && - /* This uses hashed inode numbers, so ino_bits doesn't matter. */ !supported_iv_ino_lblk_policy(policy, inode, "IV_INO_LBLK_32", - INT_MAX, 32)) + 32, 32)) return false; if (memchr_inv(policy->__reserved, 0, sizeof(policy->__reserved))) {