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([2405:201:682f:383f:9626:1a7c:c4cf:3e3b]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a428ecb61sm33556442eec.10.2026.11.02.06.14.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 06:15:02 -0800 (PST) From: Deepanshu Kartikey To: mchehab@kernel.org, sakari.ailus@linux.intel.com, laurent.pinchart@ideasonboard.com, hverkuil@kernel.org Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+54648a6c1187a7ef46a6@syzkaller.appspotmail.com Subject: [PATCH 1/2] media: em28xx: clear dev->v4l2 on v4l2 init failure Date: Mon, 2 Nov 2026 19:44:38 +0530 Message-ID: <20261102141439.13505-2-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261102141439.13505-1-kartikey406@gmail.com> References: <20261102141439.13505-1-kartikey406@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit If em28xx_v4l2_init() fails after registering the video devices (for example in v4l2_mc_create_media_graph()), the unregister_dev error path drops the initial v4l2_device reference but leaves dev->v4l2 set. If userspace still holds an open file handle to a video node, the structure stays alive. On USB disconnect, em28xx_v4l2_fini() sees the non-NULL dev->v4l2 and drops the initial reference a second time. The refcount underflows, em28xx_free_v4l2() frees struct em28xx_v4l2, and the later close() makes v4l2_device_release() touch a media entity in freed memory: BUG: KASAN: slab-use-after-free in dev_dbg_obj+0x630/0x830 Read of size 4 at addr ffff888023601bd0 by task v4l_id/6384 Clear dev->v4l2 in the error path after dropping the initial reference, so that em28xx_v4l2_fini() returns early and does not put it again. Fixes: 288254383674 ("media: em28xx: use v4l2_device release callback") Reported-by: syzbot+54648a6c1187a7ef46a6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=54648a6c1187a7ef46a6 Signed-off-by: Deepanshu Kartikey --- drivers/media/usb/em28xx/em28xx-video.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c index 84424284d486..ec4ed2b0e5fd 100644 --- a/drivers/media/usb/em28xx/em28xx-video.c +++ b/drivers/media/usb/em28xx/em28xx-video.c @@ -3137,6 +3137,7 @@ static int em28xx_v4l2_init(struct em28xx *dev) * v4l2_device refcount to zero. */ v4l2_device_put(&v4l2->v4l2_dev); + dev->v4l2 = NULL; return ret; } -- 2.43.0