From nobody Tue Sep 9 22:10:02 2025 Received: from madrid.collaboradmins.com (madrid.collaboradmins.com [46.235.227.194]) (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 452603B19B for ; Fri, 5 Jan 2024 18:47:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="bC32xTjF" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1704480444; bh=fLJxMhHQEYSpt8Bqc4/bJy7tBd8v7hDnk2PHVorE3qc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bC32xTjF4i+0BoGAcr5FknxLJTdvHfAZsGZ7CI25/elJxlKVuE3vR6OrI4/hvmfCa ThiwAnjeHHzZDCJRTuX2A8OwgkO2x+1+kcDl/KxfVobeazReMlnDhpm9QhLTtOfFdo R5RnbvFX6znHhPkHoEv7fDKAfzt7Psl7QnWxYeWNUbj/ZxJxmxwUNaL6hOMbZfK0jp hXiZblVuJ9mVWrTR4w/GzjJS1IAQ2qHE5F3R7ZxexU6Zsvz0qub7pSxo3zrJsxvCs7 zVn+JG5PlHelFoc2HMTKOnOfQ1QldimrwoTjebvnpk/OtRQZK7lNR7tTn+X37ZbwTz dujX/5z5C4kCA== Received: from workpc.. (cola.collaboradmins.com [195.201.22.229]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by madrid.collaboradmins.com (Postfix) with ESMTPSA id 50EDA3782046; Fri, 5 Jan 2024 18:47:23 +0000 (UTC) From: Dmitry Osipenko To: David Airlie , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Daniel Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , =?UTF-8?q?Christian=20K=C3=B6nig?= , Qiang Yu , Steven Price , Boris Brezillon , Emma Anholt , Melissa Wen Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, virtualization@lists.linux-foundation.org Subject: [PATCH v19 25/30] drm/shmem-helper: Don't free refcounted GEM Date: Fri, 5 Jan 2024 21:46:19 +0300 Message-ID: <20240105184624.508603-26-dmitry.osipenko@collabora.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240105184624.508603-1-dmitry.osipenko@collabora.com> References: <20240105184624.508603-1-dmitry.osipenko@collabora.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Don't free shmem object if it has pages that are in use at the time of the GEM's freeing if DRM driver doesn't manage GEM/pages lifetime properly. This prevents memory corruption due to the use-after-free bug in exchange to leaking GEM. Signed-off-by: Dmitry Osipenko --- drivers/gpu/drm/drm_gem_shmem_helper.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_g= em_shmem_helper.c index e6e6e693ab95..0d95d723b90d 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -205,9 +205,15 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *s= hmem) if (obj->import_attach) drm_prime_gem_destroy(obj, shmem->sgt); =20 - drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count)); - drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count)); - drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_pin_count)); + /* + * Prevent memory corruption caused by the use-after-free bug in a + * case where shmem user erroneously holds reference to pages while + * GEM is freed by leaking the GEM. + */ + if (drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count)) || + drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count)) || + drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_pin_count))) + return; =20 drm_gem_object_release(obj); kfree(shmem); --=20 2.43.0