A null-pointer dereference can occur in usb_make_path() when called from
usbtv_querycap() (and other ioctl handlers) during device disconnection.

Oops: general protection fault, probably for non-canonical address
0xdffffc000000000a: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000050-0x0000000000000057]
RIP: 0010:usb_make_path include/linux/usb.h:985 [inline]
RIP: 0010:usbtv_querycap+0x9c/0x100
drivers/media/usb/usbtv/usbtv-video.c:612
...
Call Trace:
 <TASK>
 v4l_querycap+0x236/0x470 drivers/media/v4l2-core/v4l2-ioctl.c:1106
 __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
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94

This happens due to a race condition between the USB device disconnect
routine (usbtv_disconnect()) and V4L2 ioctls. When the device is
disconnected, usbtv_disconnect() sets usbtv->udev = NULL without holding
the usbtv->v4l2_lock mutex. Concurrently, an ioctl handler like
usbtv_querycap() can be executing under the v4l2_lock and attempt to use
usbtv->udev, leading to a crash.

To fix this, move the usbtv->udev = NULL assignment into usbtv_video_free()
and protect it with mutex_lock(&usbtv->v4l2_lock). This ensures that no
non-queue ioctl handler can run concurrently with the pointer being
nullified. If an ioctl is already running, the mutex will block the
disconnect path until the ioctl finishes. If an ioctl is blocked waiting
for the lock, it will acquire it after the disconnect routine releases it,
but will then check video_is_registered() (which was cleared by
vb2_video_unregister_device()) and safely return -ENODEV.

Acquiring v4l2_lock after vb2_video_unregister_device() avoids
reintroducing a historical deadlock issue, and usbtv_audio_free() remains
safe as it is called before usbtv_video_free().

Fixes: 65e6a2773d65 ("media: usbtv: Remove useless locks in usbtv_video_free()")
Cc: stable@vger.kernel.org
Assisted-by: Gemini:gemini-3.6-flash Gemini:gemini-3.1-pro-preview syzbot
Reported-by: syzbot+37a57a84893052ab6071@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=37a57a84893052ab6071
Link: https://syzkaller.appspot.com/ai_job?id=5abbe65a-5853-4bc2-9135-5c75f88d51ed
Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

usbtv_probe() allocates usbtv before usbtv_video_init() registers its
embedded v4l2_device. v4l2_device_register() initializes the reference
count to one, with usbtv_release() providing the final cleanup.

If video_register_device() fails, usbtv_video_init() unregisters the
V4L2 device and returns an error without dropping the initial
v4l2_device reference. The probe error path then calls kfree() on usbtv
directly, leaving the reference stranded and bypassing
usbtv_release().

Leave the initialized V4L2 device intact on this failure path. After
releasing the USB reference, call v4l2_device_put() so the final
reference invokes usbtv_release(). Retain the direct kfree() path for
failures that occur before v4l2_device_register().

This issue was found by a static analysis tool I am developing.

Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

The ALSA PCM callbacks store the driver state in pcm->private_data. An
open PCM file can outlive USB disconnect because usbtv_audio_free() uses
snd_card_free_when_closed(). The disconnect path can then drop the V4L2
device reference and free struct usbtv before ALSA releases the substream,
so a later close dereferences freed memory in snd_usbtv_pcm_close().

Take a V4L2 device reference for the ALSA card and drop it from the card
private_free callback. This keeps struct usbtv valid until ALSA has closed
the remaining files and freed the card.

Closes: https://lore.kernel.org/r/178144969601.60470.4852887710381872458@gmail.com
Fixes: 63ddf68de52e ("[media] usbtv: add audio support")
Cc: stable@vger.kernel.org
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

Driver core holds a reference to the USB interface and its parent USB
device while the interface is bound to a driver and there is no need to
take additional references unless the structures are needed after
disconnect.

Drop the redundant device reference to reduce cargo culting, make it
easier to spot drivers where an extra reference is needed, and reduce
the risk of memory leaks when drivers fail to release it.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

This was done entirely with mindless brute force, using

    git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
        xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'

to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.

Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.

For the same reason the 'flex' versions will be done as a separate
conversion.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:

Single allocations:	kmalloc(sizeof(TYPE), ...)
are replaced with:	kmalloc_obj(TYPE, ...)

Array allocations:	kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with:	kmalloc_objs(TYPE, COUNT, ...)

Flex array allocations:	kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with:	kmalloc_flex(*PTR, FAM, COUNT, ...)

(where TYPE may also be *VAR)

The resulting allocations no longer return "void *", instead returning
"TYPE *".

Signed-off-by: Kees Cook <kees@kernel.org>

When an program is streaming (ffplay) and another program (qv4l2)
changes the TV standard from NTSC to PAL, the kernel crashes due to trying
to copy to unmapped memory.

Changing from NTSC to PAL increases the resolution in the usbtv struct,
but the video plane buffer isn't adjusted, so it overflows.

Fixes: 0e0fe3958fdd13d ("[media] usbtv: Add support for PAL video source")
Cc: stable@vger.kernel.org
Signed-off-by: Ludwig Disterhof <ludwig@disterhof.eu>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
[hverkuil: call vb2_is_busy instead of vb2_is_streaming]

Since commit 88785982a19d ("media: vb2: use lock if wait_prepare/finish
are NULL") it is no longer needed to set the wait_prepare/finish
vb2_ops callbacks as long as the lock field in vb2_queue is set.

Since the vb2_ops_wait_prepare/finish callbacks already rely on that field,
we can safely drop these callbacks.

This simplifies the code and this is a step towards the goal of deleting
these callbacks.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>

Remove locks calls in usbtv_video_free() because
are useless and may led to a deadlock as reported here:
https://syzkaller.appspot.com/x/bisect.txt?x=166dc872180000
Also remove usbtv_stop() call since it will be called when
unregistering the device.

Before 'c838530d230b' this issue would only be noticed if you
disconnect while streaming and now it is noticeable even when
disconnecting while not streaming.

Fixes: c838530d230b ("media: media videobuf2: Be more flexible on the number of queue stored buffers")
Fixes: f3d27f34fdd7 ("[media] usbtv: Add driver for Fushicai USBTV007 video frame grabber")

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Tested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil: fix minor spelling mistake in log message]

Use vb2_get_num_buffers() to avoid using queue num_buffers field directly.
This allows us to change how the number of buffers is computed in the
future.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>