CVE-2026-68213: media: rtl2832_sdr: Return queued buffers on start_streaming() failure

In the Linux kernel, the following vulnerability has been resolved:

media: rtl2832sdr: Return queued buffers on startstreaming() failure

The vb2 framework hands buffers to the driver via bufqueue() before calling startstreaming(). If startstreaming() returns an error without first returning those buffers via vb2bufferdone(), vb2startstreaming() fires WARNON(ownedbydrvcount) and the queued buffers leak.

rtl2832sdrstartstreaming() had multiple error paths that hit this trap: two direct early returns (-ENODEV, -ERESTARTSYS), plus six goto err paths covering subdev spower, tuner setup, ADC setup, stream-buffer allocation, urb allocation, and urb submission failures. None of them returned the queued buffers.

The original function had no distinct success exit and fell straight through into the err label, which previously only did mutexunlock and "return ret". Adding queued-buffer cleanup at err must therefore be paired with an explicit success return; otherwise every successful start would also drain the buffer queue and kill streaming. Add that success return, then add rtl2832sdrcleanupqueuedbufs() at the err label and before each early return.

The cleanup helper takes a vb2bufferstate argument so that the startstreaming error paths can pass VB2BUFSTATEQUEUED (as expected by userspace on startstreaming failure) while stopstreaming keeps its existing VB2BUFSTATEERROR semantics.

This mirrors the uvcvideo fix in commit 4cf3b6fd54eb ("media: uvcvideo: Return queued buffers on startstreaming() failure").

The err label still does not roll back powerctrl(), frontendctrl(), the POWERON flag, or stream/URB allocations that may have happened before the failing step. Those are pre-existing leaks of a different class and are not addressed here.