From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 B60C7398915 for ; Thu, 13 Aug 2026 18:21:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786645301; cv=none; b=fMMnUc8l6CWf6G+XHnevvMR+aXuCA8AhVDj80FQTZJMaIWWlELFrUdPPbW+iN9/sFSTbyi6mnEBxg5gu8DAVfrWJFKFtoBGzB57xKBvxXb6xl52vM7r35qAzPME9+77hwgrZjvXhVZ4VRjNacXfN5Pn1d3Y54sn7it0jHNuAMCU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786645301; c=relaxed/simple; bh=/pMbq9IQql6wvD+RCsyAyR1meLf35txTSWVbG1mrYXA=; h=From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type:Date; b=M9ijbzBUIxDSyWWWVKA637T5RcSeDGJqzaIuIqNSIEg72xiAjOTYwxeIohz3OuHVtITVamUd9myX9pOgwYHTxdupOvBZx1OCf8i0q3k3TmzK7/erwvncw14uNilaYEVP0aaOC1I3gDmegfu3bXa+FhGPFHfny0RAMP4ginoCsBM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TcvwZu6j; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TcvwZu6j" Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id 2CAC11F000E9; Thu, 13 Aug 2026 18:21:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786645299; bh=g2w9U7e77YAR/Cms4A+GYJ11YStbRKXT6qQrvUmSwH4=; h=From:To:Cc:Subject:Date; b=TcvwZu6jYK5EOO3fHGz257vW06e1u9hx4A3TiT6J5z2MYsTeMiNhpUJVtGOUl8Sm6 LeIGstj4197WPXqgZyxATOKWnwOxtLopOKL3ui5pM0J7XM0OyhMsql0Vzn1Yi8K1M4 hVxZ+72mRbRbKjvk50UpIb39Rz9ChP59QZW8GR+SjZBIjK5VK8Mivxrw2jL2r6l6On CdBM0FJFqO8URXbZAXYuXzqpw5Eyg1FtfkW7b/kNAklS9KhX8SG/6RwvSfQtvCtqy3 f6XfZcqKRYNcLdBIgn+43ffWOJuDmSHrUgMGjDN7u5ab6fQreZ07N4L0UniSZFp4yX o/Hy2SmoiWqIg== From: "syzbot" To: syzkaller-upstream-moderation@googlegroups.com Cc: nogikh@google.com, syzbot@lists.linux.dev Subject: [PATCH RFC v4] usb: gadget: uvc: check endpoint enabled state in uvcg_video_enable() Message-ID: Precedence: bulk X-Mailing-List: syzbot@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Date: Thu, 13 Aug 2026 18:21:39 +0000 (UTC) A NULL pointer dereference can occur in uvc_video_prep_requests() if userspace issues a VIDIOC_STREAMON ioctl before the USB host has fully configured the streaming endpoint. When userspace calls VIDIOC_STREAMON, the driver handles it in uvc_v4l2_streamon(), which in turn calls uvcg_video_enable(). Currently, uvcg_video_enable() only checks if the endpoint pointer is allocated (video->ep == NULL), but it fails to check if the endpoint is actually enabled (video->ep->enabled). The endpoint descriptor (video->ep->desc) is only assigned when the USB host explicitly selects the streaming alternate setting via a SET_INTERFACE control request. If userspace prematurely calls VIDIOC_STREAMON before the host has selected the streaming alternate setting, video->ep->desc will still be NULL. Because uvcg_video_enable() does not verify the endpoint's enabled state, it proceeds to call uvc_video_alloc_requests() and then uvc_video_prep_requests(). Inside uvc_video_prep_requests(), the code unconditionally dereferences video->ep->desc, resulting in a KASAN null-ptr-deref / general protection fault: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:usb_endpoint_xfer_isoc include/uapi/linux/usb/ch9.h:571 [inline] RIP: 0010:uvc_video_prep_requests drivers/usb/gadget/function/uvc_video.c:508 [inline] RIP: 0010:uvc_video_alloc_requests drivers/usb/gadget/function/uvc_video.c:559 [inline] RIP: 0010:uvcg_video_enable+0x142/0xe70 drivers/usb/gadget/function/uvc_video.c:784 Call Trace: uvc_v4l2_streamon+0x7e/0x110 drivers/usb/gadget/function/uvc_v4l2.c:531 __video_do_ioctl+0x8af/0xc70 drivers/media/v4l2-core/v4l2-ioctl.c:3133 video_usercopy+0x860/0x1430 drivers/media/v4l2-core/v4l2-ioctl.c:3475 v4l2_ioctl+0x18d/0x1e0 drivers/media/v4l2-core/v4l2-dev.c:366 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 To fix this, update uvcg_video_enable() to also verify that the endpoint is enabled (!video->ep->enabled). This ensures that if userspace prematurely calls VIDIOC_STREAMON, the driver will safely reject the request with -ENODEV instead of crashing the kernel. Fixes: 48dbe731171e ("usb: gadget: uvc: set req_size and n_requests based on the frame interval") Assisted-by: Gemini:gemini-3.6-flash Gemini:gemini-3.1-pro-preview syzbot Reported-by: syzbot+44835f0858f11e3e923c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=44835f0858f11e3e923c Link: https://syzkaller.appspot.com/ai_job?id=6bcd0cc3-0532-4cbc-81bd-e487719ff9a3 To: "Greg Kroah-Hartman" To: To: "Michael Grzeschik" Cc: "Frank Li" Cc: "Jimmy Hu" Cc: "Kees Cook" Cc: Cc: "Muhammad Bilal" Cc: "Junzhong Pan" Cc: "Xu Yang" --- v4: - Return 0 early in uvc_v4l2_streamon() if state is already UVC_STATE_STREAMING. v3: - Removed redundant video->ep->desc checks in uvcg_video_enable() and uvc_video_alloc_requests(). - Dropped uvc->state transition changes in uvc_v4l2_streamon(). https://lore.kernel.org/all/7055a5f1-3cf0-4ead-ad20-e63879247c29@mail.kernel.org/T/ v2: - Check that uvc->state is UVC_STATE_CONNECTED in uvc_v4l2_streamon() before allowing streaming. - Update uvc->state to UVC_STATE_STREAMING before calling uvcg_video_enable(), and revert it on failure. - Check video->ep->desc in addition to video->ep->enabled in uvcg_video_enable(). - Add safety checks for video->ep, video->ep->enabled, and video->ep->desc in uvc_video_alloc_requests(). https://lore.kernel.org/all/0062e956-a8d4-4c8e-a25e-4deb5ff85b4b@mail.kernel.org/T/ v1: https://lore.kernel.org/all/f345b3ad-4dff-4a90-8a9e-672979e4a8ba@mail.kernel.org/T/ --- diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c index dfa0521a2..da857c2c5 100644 --- a/drivers/usb/gadget/function/uvc_v4l2.c +++ b/drivers/usb/gadget/function/uvc_v4l2.c @@ -527,6 +527,12 @@ uvc_v4l2_streamon(struct file *file, void *fh, enum v4l2_buf_type type) if (type != video->queue.queue.type) return -EINVAL; + if (uvc->state == UVC_STATE_STREAMING) + return 0; + + if (uvc->state != UVC_STATE_CONNECTED) + return -ENODEV; + /* Enable UVC video. */ ret = uvcg_video_enable(video); if (ret < 0) diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c index 2f9700b3f..d4aeedacc 100644 --- a/drivers/usb/gadget/function/uvc_video.c +++ b/drivers/usb/gadget/function/uvc_video.c @@ -764,7 +764,7 @@ int uvcg_video_enable(struct uvc_video *video) { int ret; - if (video->ep == NULL) { + if (video->ep == NULL || !video->ep->enabled) { uvcg_info(&video->uvc->func, "Video enable failed, device is uninitialized.\n"); return -ENODEV; base-commit: db2ddb87143519e20a95aa36c60b36107b736a58 -- This is an AI-generated patch subject to moderation. 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