From: Eric Biggers <ebiggers@kernel.org>
To: Chris Mason <clm@fb.com>
Cc: linux-fscrypt@vger.kernel.org
Subject: Re: max fsverity descriptor size?
Date: Wed, 2 Dec 2020 10:12:51 -0800 [thread overview]
Message-ID: <X8fZI93Agr4f4Lwh@sol.localdomain> (raw)
In-Reply-To: <7F52BBF2-46A8-4854-9B68-1DC3EFA12EF0@fb.com>
+linux-fscrypt
On Wed, Dec 02, 2020 at 09:01:52AM -0500, Chris Mason wrote:
> Hi Eric,
>
> I’m working on fsverity support in btrfs and wanted to check on the max size
> of the descriptor. I can go up to any size, just wanted to make sure I had
> things correct in the disk format.
>
> -chris
The implementations of fs-verity in ext4 and f2fs store the built-in signature
(if there is one) appended to the 'struct fsverity_descriptor', and limit the
total size of those two things combined to 16384 bytes. See
FS_VERITY_MAX_DESCRIPTOR_SIZE in fs/verity/fsverity_private.h.
Note that there's nothing special about this particular number; it's just an
implementation limit to prevent userspace doing weird things with megabytes
"signatures".
If btrfs will be storing built-in signatures in the same way, it probably should
use the same limit. Preferably it would be done in a way such that it's
possible to increase the limit later if it's ever needed.
- Eric
next parent reply other threads:[~2020-12-02 18:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <7F52BBF2-46A8-4854-9B68-1DC3EFA12EF0@fb.com>
2020-12-02 18:12 ` Eric Biggers [this message]
2020-12-02 18:33 ` max fsverity descriptor size? Chris Mason
2020-12-02 18:44 ` Eric Biggers
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