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-3.5-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=e3902952-fe28-4ca4-a910-c485a9927925 To: "Greg Kroah-Hartman" To: To: "Michael Grzeschik" Cc: "Frank Li" Cc: "Jimmy Hu" Cc: "Hans Verkuil" Cc: "Kees Cook" Cc: "Laurent Pinchart" Cc: Cc: "Muhammad Bilal" Cc: "Junzhong Pan" Cc: "Xu Yang" --- 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(). 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..a80663c9a 100644 --- a/drivers/usb/gadget/function/uvc_v4l2.c +++ b/drivers/usb/gadget/function/uvc_v4l2.c @@ -527,17 +527,24 @@ 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_CONNECTED) + return -ENODEV; + + uvc->state = UVC_STATE_STREAMING; + /* Enable UVC video. */ ret = uvcg_video_enable(video); - if (ret < 0) + if (ret < 0) { + if (uvc->state == UVC_STATE_STREAMING) + uvc->state = UVC_STATE_CONNECTED; return ret; + } /* * Complete the alternate setting selection setup phase now that * userspace is ready to provide video frames. */ uvc_function_setup_continue(uvc, 0); - uvc->state = UVC_STATE_STREAMING; return 0; } diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c index 2f9700b3f..bd67a9d80 100644 --- a/drivers/usb/gadget/function/uvc_video.c +++ b/drivers/usb/gadget/function/uvc_video.c @@ -551,6 +551,9 @@ uvc_video_alloc_requests(struct uvc_video *video) unsigned int i; int ret = -ENOMEM; + if (video->ep == NULL || !video->ep->enabled || !video->ep->desc) + return -ENODEV; + /* * calculate in uvc_video_prep_requests * - video->uvc_num_requests @@ -764,7 +767,7 @@ int uvcg_video_enable(struct uvc_video *video) { int ret; - if (video->ep == NULL) { + if (video->ep == NULL || !video->ep->enabled || !video->ep->desc) { 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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