9909ce33f9
V4L2 allows buffer queueing before streamon while libcamera does not.
The compatibility layer thus saves these buffers in a pending queue
until streamon, and then automatically queues them. However, this
pending queue is not cleared when the buffers are freed, so the
following sequence of actions will cause a use-after-free:
1. queue buffers
2. free buffers
- buffers from 1. stay in pending queue but have been freed
3. queue buffers
4. streamon
- buffers from 1. are enqueued, then the buffers from 3. are
enqueued. Use-after-free segfault when libcamera tries to handle
the enqueued buffers from 1.
Fix this by clearing the pending request queue upon buffers being freed.
Also clear the pending request queue on streamOff, for correctness.
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
.. SPDX-License-Identifier: CC-BY-SA-4.0
.. section-begin-libcamera
===========
libcamera
===========
**A complex camera support library for Linux, Android, and ChromeOS**
Cameras are complex devices that need heavy hardware image processing
operations. Control of the processing is based on advanced algorithms that must
run on a programmable processor. This has traditionally been implemented in a
dedicated MCU in the camera, but in embedded devices algorithms have been moved
to the main CPU to save cost. Blurring the boundary between camera devices and
Linux often left the user with no other option than a vendor-specific
closed-source solution.
To address this problem the Linux media community has very recently started
collaboration with the industry to develop a camera stack that will be
open-source-friendly while still protecting vendor core IP. libcamera was born
out of that collaboration and will offer modern camera support to Linux-based
systems, including traditional Linux distributions, ChromeOS and Android.
.. section-end-libcamera
.. section-begin-getting-started
Getting Started
---------------
To fetch the sources, build and install:
::
git clone git://linuxtv.org/libcamera.git
cd libcamera
meson build
ninja -C build install
Dependencies
~~~~~~~~~~~~
The following Debian/Ubuntu packages are required for building libcamera.
Other distributions may have differing package names:
A C++ toolchain: [required]
Either {g++, clang}
for libcamera: [required]
meson (>= 0.47) ninja-build python3-yaml
If your distribution doesn't provide a recent enough version of meson,
you can install or upgrade it using pip3.
.. code::
pip3 install --user meson
pip3 install --user --upgrade meson
for device hotplug enumeration: [optional]
pkg-config libudev-dev
for documentation: [optional]
python3-sphinx doxygen
for gstreamer: [optional]
libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev
for IPA module signing: [required]
libgnutls28-dev openssl
for qcam: [optional]
qtbase5-dev libqt5core5a libqt5gui5 libqt5widgets5
Using GStreamer plugin
~~~~~~~~~~~~~~~~~~~~~~
To use GStreamer plugin from source tree, set the following environment so that
GStreamer can find it.
export GST_PLUGIN_PATH=$(pwd)/build/src/gstreamer
The debugging tool `gst-launch-1.0` can be used to construct and pipeline and test
it. The following pipeline will stream from the camera named "Camera 1" onto the
default video display element on your system.
.. code::
gst-launch-1.0 libcamerasrc camera-name="Camera 1" ! videoconvert ! autovideosink
.. section-end-getting-started