linux-hardening - Re: [PATCH v4][next] xfs: Replace one-element arrays with flexible-array members

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Message-ID: <f074c562-774d-fb35-b6a2-01c3873bb6ec@intel.com>
Date:   Wed, 14 Jul 2021 17:27:54 +0800
From:   "Chen, Rong A" <rong.a.chen@...el.com>
To:     Christoph Hellwig <hch@...radead.org>,
        "Darrick J. Wong" <djwong@...nel.org>
Cc:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v4][next] xfs: Replace one-element arrays with
 flexible-array members



On 4/14/2021 12:53 AM, Christoph Hellwig wrote:
> On Mon, Apr 12, 2021 at 08:48:08AM -0700, Darrick J. Wong wrote:
>> A couple of revisions ago I specifically asked Gustavo to create these
>> 'silly' sizeof helpers to clean up...
>>
>>>> -					(sizeof(struct xfs_efd_log_item) +
>>>> -					(XFS_EFD_MAX_FAST_EXTENTS - 1) *
>>>> -					sizeof(struct xfs_extent)),
>>>> -					0, 0, NULL);
>>>> +					 struct_size((struct xfs_efd_log_item *)0,
>>>> +					 efd_format.efd_extents,
>>>> +					 XFS_EFD_MAX_FAST_EXTENTS),
>>
>> ...these even uglier multiline statements.  I was also going to ask for
>> these kmem cache users to get cleaned up.  I'd much rather look at:
>>
>> 	xfs_efi_zone = kmem_cache_create("xfs_efi_item",
>> 				sizeof_xfs_efi(XFS_EFI_MAX_FAST_EXTENTS), 0);
>> 	if (!xfs_efi_zone)
>> 		goto the_drop_zone;
>>
>> even if it means another static inline.
> 
> Which doesn't really work with struct_size or rather leads to a mess
> like the above as struct_size really wants a variable and not just a
> type.  Making it really nasty for both allocations and creating slab
> caches.  I tried to find a workaround for that, but that makes the
> compiler unhappy based its inlining heuristics.
> 
> Anyway, a lot of the helpers are pretty silly as they duplicate stuff
> without cleaning up the underlying mess.  I tried to sort much of this
> out here, still WIP:
> 
> http://git.infradead.org/users/hch/xfs.git/shortlog/refs/heads/xfs-array-size
> 

Hi xfs maintainers,

Kindly ping, is there any new progress on this patch series?

Best Regards,
Rong Chen