linux-kernel - Re: [PATCH -next v2] fs-verity: Use struct_size() helper in enable

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Date:   Wed, 18 May 2022 20:17:59 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Zhang Jianhua <chris.zjh@...wei.com>
Cc:     tytso@....edu, linux-fscrypt@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next v2] fs-verity: Use struct_size() helper in
 enable_verity()

On Wed, May 18, 2022 at 08:06:04PM -0700, Eric Biggers wrote:
> On Thu, May 19, 2022 at 10:24:50AM +0800, Zhang Jianhua wrote:
> > Also, address the following sparse warning:
> > fs/verity/enable.c:205:28: warning: using sizeof on a flexible structure
> 
> How can I reproduce this warning?  I am using the latest version of sparse, and
> I don't see any of these warnings you're reporting.
> 
> $ sparse --version
> v0.6.4
> $ make C=2 fs/verity/
>   CHECK   scripts/mod/empty.c
>   CALL    scripts/checksyscalls.sh
>   CALL    scripts/atomic/check-atomics.sh
>   DESCEND objtool
>   CHECK   fs/verity/enable.c
>   CHECK   fs/verity/hash_algs.c
>   CHECK   fs/verity/init.c
>   CHECK   fs/verity/measure.c
>   CHECK   fs/verity/open.c
>   CHECK   fs/verity/read_metadata.c
>   CHECK   fs/verity/verify.c
>   CHECK   fs/verity/signature.c
> 

'make C=2 CHECK="sparse -Wflexible-array-sizeof"' does the trick.  However, it
produces a *lot* of warnings all over the place.

Unless there is an effort to actually address all of these so that this warning
can be enabled by default, I don't see the poinnt in addressing these just for
the warnings sake.  The change to fsverity_ioctl_measure() is definitely just
for the warning's sake, so I don't really want to do that one.  The change to
enable_verity() is a bit less useless, so I could still take that one.

- Eric