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([2a01:e0a:106d:1080:1d4b:274c:94d:a69f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45da15a5653sm43847302f8f.35.2026.05.19.00.23.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 May 2026 00:23:36 -0700 (PDT) Message-ID: <6db86d54-b463-49bb-ae7f-35c694e624bc@linaro.org> Date: Tue, 19 May 2026 09:23:35 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Neil Armstrong Reply-To: Neil Armstrong Subject: Re: [PATCH 02/13] drm/meson: dw-hdmi: Protect from possible NULL pointer dereference To: Jonas Karlman , Kevin Hilman , Heiko Stuebner , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jerome Brunet , Martin Blumenstingl , Sam Ravnborg Cc: dri-devel@lists.freedesktop.org, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org References: <20260518194744.2483580-1-jonas@kwiboo.se> <20260518194744.2483580-3-jonas@kwiboo.se> Content-Language: en-US, fr Autocrypt: addr=neil.armstrong@linaro.org; keydata= xsBNBE1ZBs8BCAD78xVLsXPwV/2qQx2FaO/7mhWL0Qodw8UcQJnkrWmgTFRobtTWxuRx8WWP GTjuhvbleoQ5Cxjr+v+1ARGCH46MxFP5DwauzPekwJUD5QKZlaw/bURTLmS2id5wWi3lqVH4 BVF2WzvGyyeV1o4RTCYDnZ9VLLylJ9bneEaIs/7cjCEbipGGFlfIML3sfqnIvMAxIMZrvcl9 qPV2k+KQ7q+aXavU5W+yLNn7QtXUB530Zlk/d2ETgzQ5FLYYnUDAaRl+8JUTjc0CNOTpCeik 80TZcE6f8M76Xa6yU8VcNko94Ck7iB4vj70q76P/J7kt98hklrr85/3NU3oti3nrIHmHABEB AAHNKk5laWwgQXJtc3Ryb25nIDxuZWlsLmFybXN0cm9uZ0BsaW5hcm8ub3JnPsLAkQQTAQoA OwIbIwULCQgHAwUVCgkICwUWAgMBAAIeAQIXgBYhBInsPQWERiF0UPIoSBaat7Gkz/iuBQJk Q5wSAhkBAAoJEBaat7Gkz/iuyhMIANiD94qDtUTJRfEW6GwXmtKWwl/mvqQtaTtZID2dos04 YqBbshiJbejgVJjy+HODcNUIKBB3PSLaln4ltdsV73SBcwUNdzebfKspAQunCM22Mn6FBIxQ GizsMLcP/0FX4en9NaKGfK6ZdKK6kN1GR9YffMJd2P08EO8mHowmSRe/ExAODhAs9W7XXExw UNCY4pVJyRPpEhv373vvff60bHxc1k/FF9WaPscMt7hlkbFLUs85kHtQAmr8pV5Hy9ezsSRa GzJmiVclkPc2BY592IGBXRDQ38urXeM4nfhhvqA50b/nAEXc6FzqgXqDkEIwR66/Gbp0t3+r yQzpKRyQif3OwE0ETVkGzwEIALyKDN/OGURaHBVzwjgYq+ZtifvekdrSNl8TIDH8g1xicBYp QTbPn6bbSZbdvfeQPNCcD4/EhXZuhQXMcoJsQQQnO4vwVULmPGgtGf8PVc7dxKOeta+qUh6+ SRh3vIcAUFHDT3f/Zdspz+e2E0hPV2hiSvICLk11qO6cyJE13zeNFoeY3ggrKY+IzbFomIZY 4yG6xI99NIPEVE9lNBXBKIlewIyVlkOaYvJWSV+p5gdJXOvScNN1epm5YHmf9aE2ZjnqZGoM Mtsyw18YoX9BqMFInxqYQQ3j/HpVgTSvmo5ea5qQDDUaCsaTf8UeDcwYOtgI8iL4oHcsGtUX oUk33HEAEQEAAcLAXwQYAQIACQUCTVkGzwIbDAAKCRAWmrexpM/4rrXiB/sGbkQ6itMrAIfn M7IbRuiSZS1unlySUVYu3SD6YBYnNi3G5EpbwfBNuT3H8//rVvtOFK4OD8cRYkxXRQmTvqa3 3eDIHu/zr1HMKErm+2SD6PO9umRef8V82o2oaCLvf4WeIssFjwB0b6a12opuRP7yo3E3gTCS KmbUuLv1CtxKQF+fUV1cVaTPMyT25Od+RC1K+iOR0F54oUJvJeq7fUzbn/KdlhA8XPGzwGRy 4zcsPWvwnXgfe5tk680fEKZVwOZKIEuJC3v+/yZpQzDvGYJvbyix0lHnrCzq43WefRHI5XTT QbM0WUIBIcGmq38+OgUsMYu4NzLu7uZFAcmp6h8g Organization: Linaro In-Reply-To: <20260518194744.2483580-3-jonas@kwiboo.se> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/18/26 21:47, Jonas Karlman wrote: > The IRQ handler can be called at any time after the call to > devm_request_threaded_irq() completes, even before dw_hdmi->bridge has > been assigned later in meson_dw_hdmi_bind(). > > Protect from a possible NULL pointer dereference in IRQ handler by only > calling drm_helper_hpd_irq_event() when bridge has been assigned. > > Fixes: e67f6037ae1b ("drm/meson: split out encoder from meson_dw_hdmi") > Signed-off-by: Jonas Karlman > --- > I only observed this NULL pointer dereference one time, without being > able to reliably re-create a similar timing scenario. I still think this > is an issue that possible could happen and likely should be fixed. > > Note that patches later in this series will fully replace this change. > --- > drivers/gpu/drm/meson/meson_dw_hdmi.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c > index 993f6d5d4b29..eafe7daf6ff1 100644 > --- a/drivers/gpu/drm/meson/meson_dw_hdmi.c > +++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c > @@ -520,7 +520,8 @@ static irqreturn_t dw_hdmi_top_thread_irq(int irq, void *dev_id) > u32 stat = dw_hdmi->irq_stat; > > /* HPD Events */ > - if (stat & (HDMITX_TOP_INTR_HPD_RISE | HDMITX_TOP_INTR_HPD_FALL)) { > + if (stat & (HDMITX_TOP_INTR_HPD_RISE | HDMITX_TOP_INTR_HPD_FALL) && > + dw_hdmi->bridge) { > bool hpd_connected = false; > > if (stat & HDMITX_TOP_INTR_HPD_RISE) Reviewed-by: Neil Armstrong Thanks, Neil