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Fri, 13 Nov 2026 06:56:13 -0800 (PST) Received: from cachyos-x8664 ([177.245.232.83]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-86288133265sm2844298a34.14.2026.11.13.06.56.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 06:56:13 -0800 (PST) From: Diego Fernando Mancera Gomez To: mchehab@kernel.org Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, syzbot+1a7507a194fff09e5c44@syzkaller.appspotmail.com, diegomancera.dev@gmail.com Subject: [PATCH v3] media: em28xx: clear dev->v4l2 when v4l2 init fails Date: Fri, 13 Nov 2026 08:53:59 -0600 Message-ID: <20261113145359.65440-1-diegomancera.dev@gmail.com> X-Mailer: git-send-email 2.56.1 In-Reply-To: References: X-Mailing-List: linux-media@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 In em28xx_v4l2_init(), if an error occurs after video_register_device() succeeds, the unregister_dev error path unregisters the video devices and drops the initial v4l2_dev reference, but leaves dev->v4l2 set. An em28xx_v4l2_open() call already in progress (such as from v4l_id) that blocked on dev->lock while em28xx_v4l2_init() held it will then find dev->v4l2 still non-NULL and succeed on an unregistered node instead of returning -ENODEV. When the device is later disconnected, em28xx_v4l2_fini() also sees dev->v4l2 is still set and calls v4l2_device_put() a second time, dropping the refcount to zero and freeing v4l2 while v4l_id still holds it, causing a slab-use-after-free in v4l2_open(). Fix this by clearing dev->v4l2 under dev->lock in the unregister_dev error path of em28xx_v4l2_init(). Fixes: 288254383674 ("media: em28xx: use v4l2_device release callback") Cc: stable@vger.kernel.org Reported-by: syzbot+1a7507a194fff09e5c44@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1a7507a194fff09e5c44 Signed-off-by: Diego Fernando Mancera Gomez --- Changes in v3: - Resend: v2 reached lore with the "diff --git" header line split in two, so the Media CI robot could not apply it. No code changes. Changes in v2: - Drop the non-standard 'Assisted-by: Gemini' trailer that failed checkpatch. Note: compile-tested drivers/media/usb/em28xx/em28xx-video.o with allmodconfig (no warnings); not runtime-tested locally against the syzbot reproducer. drivers/media/usb/em28xx/em28xx-video.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c index 84424284d486..f78325a41124 100644 --- a/drivers/media/usb/em28xx/em28xx-video.c +++ b/drivers/media/usb/em28xx/em28xx-video.c @@ -3129,6 +3129,12 @@ static int em28xx_v4l2_init(struct em28xx *dev) vb2_video_unregister_device(&v4l2->vdev); } + /* + * Clear dev->v4l2 to prevent an in-progress em28xx_v4l2_open() from + * succeeding on an unregistered node (returning -ENODEV instead) and + * to prevent em28xx_v4l2_fini() from tearing down the instance again. + */ + dev->v4l2 = NULL; mutex_unlock(&dev->lock); /* -- 2.56.1