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Date: Mon, 7 Sep 2020 15:51:51 -0700 From: Eric Biggers <ebiggers@...nel.org> To: linux-fscrypt@...r.kernel.org Cc: linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, Jeff Layton <jlayton@...nel.org>, Paul Crowley <paulcrowley@...gle.com> Subject: Re: [PATCH] fscrypt: restrict IV_INO_LBLK_32 to ino_bits <= 32 On Mon, Aug 24, 2020 at 01:38:41PM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@...gle.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@...nel.org> > Signed-off-by: Eric Biggers <ebiggers@...gle.com> Applied to fscrypt.git#master for 5.10. - Eric
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