From: Kees Cook <keescook@chromium.org>
To: Erick Archer <erick.archer@gmx.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@intel.com>,
Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] drm/i915: Add flex arrays to struct i915_syncmap
Date: Fri, 9 Feb 2024 23:25:16 -0800 [thread overview]
Message-ID: <202402092322.09287B8@keescook> (raw)
In-Reply-To: <20240208181318.4259-1-erick.archer@gmx.com>
On Thu, Feb 08, 2024 at 07:13:18PM +0100, Erick Archer wrote:
> The "struct i915_syncmap" uses a dynamically sized set of trailing
> elements. It can use an "u32" array or a "struct i915_syncmap *"
> array.
>
> So, use the preferred way in the kernel declaring flexible arrays [1].
> Because there are two possibilities for the trailing arrays, it is
> necessary to declare a union and use the DECLARE_FLEX_ARRAY macro.
>
> The comment can be removed as the union is now clear enough.
>
> Also, avoid the open-coded arithmetic in the memory allocator functions
> [2] using the "struct_size" macro.
>
> Moreover, refactor the "__sync_seqno" and "__sync_child" functions due
> to now it is possible to use the union members added to the structure.
> This way, it is also possible to avoid the open-coded arithmetic in
> pointers.
>
> Link: https://www.kernel.org/doc/html/next/process/deprecated.html#zero-length-and-one-element-arrays [1]
> Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [2]
> Signed-off-by: Erick Archer <erick.archer@gmx.com>
> ---
> drivers/gpu/drm/i915/i915_syncmap.c | 19 ++++++++-----------
> 1 file changed, 8 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_syncmap.c b/drivers/gpu/drm/i915/i915_syncmap.c
> index 60404dbb2e9f..df6437c37373 100644
> --- a/drivers/gpu/drm/i915/i915_syncmap.c
> +++ b/drivers/gpu/drm/i915/i915_syncmap.c
> @@ -75,13 +75,10 @@ struct i915_syncmap {
> unsigned int height;
> unsigned int bitmap;
> struct i915_syncmap *parent;
> - /*
> - * Following this header is an array of either seqno or child pointers:
> - * union {
> - * u32 seqno[KSYNCMAP];
> - * struct i915_syncmap *child[KSYNCMAP];
> - * };
> - */
> + union {
> + DECLARE_FLEX_ARRAY(u32, seqno);
> + DECLARE_FLEX_ARRAY(struct i915_syncmap *, child);
> + };
This is a new code pattern for me! Trailing arrays of different element
sizes but with a fixed element count. :)
I hope when __counted_by is expanded to take expressions we can add a
literal. :)
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
next prev parent reply other threads:[~2024-02-10 7:25 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-08 18:13 [PATCH] drm/i915: Add flex arrays to struct i915_syncmap Erick Archer
2024-02-08 18:39 ` Gustavo A. R. Silva
2024-02-10 7:25 ` Kees Cook [this message]
2024-02-12 12:01 ` Tvrtko Ursulin
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