From nobody Sat Feb 7 22:07:10 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ACF453234; Fri, 2 May 2025 00:24:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746145485; cv=none; b=J2lSLzOfZgQTJVMVRNiMLr+Ge5Bj8QNmN7OFte/s4yoWjCah7LvV3GUTN8T5npeb2ILMCXcxF6HX2g8X5+rmkpdPcfARc6dC39WnIirko7alfF7D2D316NKcKNuMsev+63PQrNQ4a4C+L2vxHLCZJxNFrctrAL7yfb80b2a1k/c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746145485; c=relaxed/simple; bh=6FeYoImvtlRRNM4YoESqUYiyq85ZDtoc2RCzztmOpcY=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version:Content-Type; b=d2M34kMfBYIPOJaFX/M8iItZJrxvMAIxZg6XB6tLT3hFzhET4tNtbTtsQsXqW509oDEDfenHHf6V98nEKrYuM6T6CcAGxoO2x7tJNOBElAnsi0LPVvxGt+833v2U3lLvpnPv8rQnqi7BbGV56G9wxE5mpQ3nMzsA8dhGHo6ae78= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HYPplRKQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HYPplRKQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2E9D2C4CEE3; Fri, 2 May 2025 00:24:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746145484; bh=6FeYoImvtlRRNM4YoESqUYiyq85ZDtoc2RCzztmOpcY=; h=From:To:Cc:Subject:Date:From; b=HYPplRKQY1aF1RJXH+LDpHGC00zMlBUO748oRhW6OW+9uPXIFH1Qvc4c9+wSHP7QA XlsaUYmaJY8GX++jSCVqdjCSAR5SvFSrMYzV73WxzSWupC10+T63vNA8pXKU8kxbNW 5mRkDkxDgHOPO96NYPeqYZ9Osy7wxMFzvI+byRpMvh8d/HXaX+F3okZ1AM6fhNYSke khHDKwF8k1pun+HnZOnrQ7WKmodA4RUPUf9lyoPh9t2bYhTlNh0v4O+KTeZBogKMbo M6tzu7SaG+/WLo64cIWwTKId809m7B1+ifZiOPbCAGCLDtJ17IHMI8oxnGjn5TdAS8 EhCrzy3kAlHhQ== From: Kees Cook To: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= Cc: Kees Cook , Matthew Brost , Christian Koenig , Somalapuram Amaranath , Huang Rui , Matthew Auld , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v2] drm/ttm: Silence randstruct warning about casting struct file Date: Thu, 1 May 2025 17:24:38 -0700 Message-Id: <20250502002437.it.851-kees@kernel.org> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Developer-Signature: v=1; a=openpgp-sha256; l=2280; i=kees@kernel.org; h=from:subject:message-id; bh=6FeYoImvtlRRNM4YoESqUYiyq85ZDtoc2RCzztmOpcY=; b=owGbwMvMwCVmps19z/KJym7G02pJDBkiAkc5ExuSPvH/Cog4tZ3VTjb98WqR6MUzm+ZMmsv+K upDQKZ5RykLgxgXg6yYIkuQnXuci8fb9nD3uYowc1iZQIYwcHEKwEQ+/2X47/WwaLNgcHXbvzNJ tcdVU3klsv9Ftc1g2ijPaWbzveGhAMP/cFbe763qS79FVQg8zHlt+ef9xTsqkvrWwnGdinOVePw ZAQ== X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Casting through a "void *" isn't sufficient to convince the randstruct GCC plugin that the result is intentional. Instead operate through an explicit union to silence the warning: drivers/gpu/drm/ttm/ttm_backup.c: In function 'ttm_file_to_backup': drivers/gpu/drm/ttm/ttm_backup.c:21:16: note: randstruct: casting between r= andomized structure pointer types (ssa): 'struct ttm_backup' and 'struct fi= le' 21 | return (void *)file; | ^~~~~~~~~~~~ Suggested-by: Matthew Brost Fixes: e7b5d23e5d47 ("drm/ttm: Provide a shmem backup implementation") Signed-off-by: Kees Cook Reviewed-by: Matthew Brost --- v2: use struct and container_of (matthew) v1: https://lore.kernel.org/all/20250501195859.work.107-kees@kernel.org/ Cc: Thomas Hellstr=C3=B6m Cc: Christian Koenig Cc: Somalapuram Amaranath Cc: Matthew Brost Cc: Huang Rui Cc: Matthew Auld Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Simona Vetter Cc: --- drivers/gpu/drm/ttm/ttm_backup.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_backup.c b/drivers/gpu/drm/ttm/ttm_bac= kup.c index 93c007f18855..60cff6c60db4 100644 --- a/drivers/gpu/drm/ttm/ttm_backup.c +++ b/drivers/gpu/drm/ttm/ttm_backup.c @@ -9,16 +9,21 @@ =20 /* * Casting from randomized struct file * to struct ttm_backup * is fine si= nce - * struct ttm_backup is never defined nor dereferenced. + * struct ttm_backup is never defined nor dereferenced. Use a single-member + * struct to avoid cast warnings. */ +struct ttm_backup { + struct file file; +}; + static struct file *ttm_backup_to_file(struct ttm_backup *backup) { - return (void *)backup; + return &backup->file; } =20 static struct ttm_backup *ttm_file_to_backup(struct file *file) { - return (void *)file; + return container_of(file, struct ttm_backup, file); } =20 /* --=20 2.34.1