From: Satya Tangirala <satyat@google.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
linux-ext4@vger.kernel.org,
Barani Muthukumaran <bmuthuku@qti.qualcomm.com>,
Kuohong Wang <kuohong.wang@mediatek.com>,
Kim Boojin <boojin.kim@samsung.com>,
Eric Biggers <ebiggers@google.com>
Subject: Re: [PATCH v10 02/12] block: Keyslot Manager for Inline Encryption
Date: Tue, 28 Apr 2020 02:14:41 +0000 [thread overview]
Message-ID: <20200428021441.GA52406@google.com> (raw)
In-Reply-To: <20200422092250.GA12290@infradead.org>
On Wed, Apr 22, 2020 at 02:22:50AM -0700, Christoph Hellwig wrote:
> > +bool blk_ksm_crypto_cfg_supported(struct blk_keyslot_manager *ksm,
> > + const struct blk_crypto_config *cfg)
> > +{
> > + if (!ksm)
> > + return false;
> > + return (ksm->crypto_modes_supported[cfg->crypto_mode] &
> > + cfg->data_unit_size) &&
> > + (ksm->max_dun_bytes_supported >= cfg->dun_bytes);
>
> Nit: why not expand this a bit to be more readable:
>
> if (!(ksm->crypto_modes_supported[cfg->crypto_mode] &
> cfg->data_unit_size))
> return false;
> if (ksm->max_dun_bytes_supported < cfg->dun_bytes)
> return false;
> return true;
>
> > +int blk_ksm_evict_key(struct blk_keyslot_manager *ksm,
> > + const struct blk_crypto_key *key)
> > +{
> > + struct blk_ksm_keyslot *slot;
> > + int err = 0;
> > +
> > + blk_ksm_hw_enter(ksm);
> > + slot = blk_ksm_find_keyslot(ksm, key);
> > + if (!slot)
> > + goto out_unlock;
> > +
> > + if (atomic_read(&slot->slot_refs) != 0) {
> > + err = -EBUSY;
> > + goto out_unlock;
> > + }
>
> This check looks racy.
Yes, this could in theory race with blk_ksm_put_slot (e.g. if it's
called while there's still IO in flight/IO that just finished) - But
it's currently only called by fscrypt when a key is being destroyed,
which only happens after all the inodes using that key are evicted, and
no data is in flight, so when this function is called, slot->slot_refs
will be 0. In particular, this function should only be called when the
key isn't being used for IO anymore. I'll add a WARN_ON_ONCE and also
make the assumption clearer. We could also instead make this wait for
the slot_refs to become 0 and then evict the key instead of just
returning -EBUSY as it does now, but I'm not sure if it's really what
we want to do/worth doing right now...
next prev parent reply other threads:[~2020-04-28 2:14 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-08 3:56 [PATCH v10 00/12] Inline Encryption Support Satya Tangirala
2020-04-08 3:56 ` [PATCH v10 01/12] Documentation: Document the blk-crypto framework Satya Tangirala
2020-04-08 3:56 ` [PATCH v10 02/12] block: Keyslot Manager for Inline Encryption Satya Tangirala
2020-04-22 9:22 ` Christoph Hellwig
2020-04-28 2:14 ` Satya Tangirala [this message]
2020-04-28 2:46 ` Eric Biggers
2020-04-28 2:57 ` Eric Biggers
2020-04-28 5:19 ` Christoph Hellwig
2020-04-08 3:56 ` [PATCH v10 03/12] block: Inline encryption support for blk-mq Satya Tangirala
2020-04-22 9:35 ` Christoph Hellwig
2020-04-28 2:54 ` Satya Tangirala
2020-04-28 5:21 ` Christoph Hellwig
2020-04-08 3:56 ` [PATCH v10 04/12] block: Make blk-integrity preclude hardware inline encryption Satya Tangirala
2020-04-08 3:56 ` [PATCH v10 05/12] block: blk-crypto-fallback for Inline Encryption Satya Tangirala
2020-04-22 9:37 ` Christoph Hellwig
2020-04-08 3:56 ` [PATCH v10 06/12] scsi: ufs: UFS driver v2.1 spec crypto additions Satya Tangirala
2020-04-08 3:56 ` [PATCH v10 07/12] scsi: ufs: UFS crypto API Satya Tangirala
2020-04-08 3:56 ` [PATCH v10 08/12] scsi: ufs: Add inline encryption support to UFS Satya Tangirala
2020-04-08 3:56 ` [PATCH v10 09/12] fs: introduce SB_INLINECRYPT Satya Tangirala
2020-04-08 3:56 ` [PATCH v10 10/12] fscrypt: add inline encryption support Satya Tangirala
2020-04-08 3:56 ` [PATCH v10 11/12] f2fs: " Satya Tangirala
2020-04-08 3:56 ` [PATCH v10 12/12] ext4: " Satya Tangirala
2020-04-08 4:18 ` [PATCH v10 00/12] Inline Encryption Support Eric Biggers
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