Pixman returns a signed int for the image width/height, but the VNC
protocol only permits a unsigned int16. Effective framebuffer size
is determined by the guest, limited by the video RAM size, so the
dimensions are unlikely to exceed the range of an unsigned int16,
but this is not currently validated.
With the current use of 'int' for client width/height, the calculation
of offsets in vnc_update_throttle_offset() suffers from integer size
promotion and sign extension, causing coverity warnings
*** CID 1385147: Integer handling issues (SIGN_EXTENSION)
/ui/vnc.c: 979 in vnc_update_throttle_offset()
973 * than that the client would already suffering awful audio
974 * glitches, so dropping samples is no worse really).
975 */
976 static void vnc_update_throttle_offset(VncState *vs)
977 {
978 size_t offset =
>>> CID 1385147: Integer handling issues (SIGN_EXTENSION)
>>> Suspicious implicit sign extension:
"vs->client_pf.bytes_per_pixel" with type "unsigned char" (8 bits,
unsigned) is promoted in "vs->client_width * vs->client_height *
vs->client_pf.bytes_per_pixel" to type "int" (32 bits, signed), then
sign-extended to type "unsigned long" (64 bits, unsigned). If
"vs->client_width * vs->client_height * vs->client_pf.bytes_per_pixel"
is greater than 0x7FFFFFFF, the upper bits of the result will all be 1.
979 vs->client_width * vs->client_height * vs->client_pf.bytes_per_pixel;
Change client_width / client_height to be a size_t to avoid sign
extension and integer promotion. Then validate that dimensions are in
range wrt the RFB protocol u16 limits.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 20180118155254.17053-1-berrange@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
QEMU README
===========
QEMU is a generic and open source machine & userspace emulator and
virtualizer.
QEMU is capable of emulating a complete machine in software without any
need for hardware virtualization support. By using dynamic translation,
it achieves very good performance. QEMU can also integrate with the Xen
and KVM hypervisors to provide emulated hardware while allowing the
hypervisor to manage the CPU. With hypervisor support, QEMU can achieve
near native performance for CPUs. When QEMU emulates CPUs directly it is
capable of running operating systems made for one machine (e.g. an ARMv7
board) on a different machine (e.g. an x86_64 PC board).
QEMU is also capable of providing userspace API virtualization for Linux
and BSD kernel interfaces. This allows binaries compiled against one
architecture ABI (e.g. the Linux PPC64 ABI) to be run on a host using a
different architecture ABI (e.g. the Linux x86_64 ABI). This does not
involve any hardware emulation, simply CPU and syscall emulation.
QEMU aims to fit into a variety of use cases. It can be invoked directly
by users wishing to have full control over its behaviour and settings.
It also aims to facilitate integration into higher level management
layers, by providing a stable command line interface and monitor API.
It is commonly invoked indirectly via the libvirt library when using
open source applications such as oVirt, OpenStack and virt-manager.
QEMU as a whole is released under the GNU General Public License,
version 2. For full licensing details, consult the LICENSE file.
Building
========
QEMU is multi-platform software intended to be buildable on all modern
Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety
of other UNIX targets. The simple steps to build QEMU are:
mkdir build
cd build
../configure
make
Additional information can also be found online via the QEMU website:
https://qemu.org/Hosts/Linux
https://qemu.org/Hosts/Mac
https://qemu.org/Hosts/W32
Submitting patches
==================
The QEMU source code is maintained under the GIT version control system.
git clone git://git.qemu.org/qemu.git
When submitting patches, the preferred approach is to use 'git
format-patch' and/or 'git send-email' to format & send the mail to the
qemu-devel@nongnu.org mailing list. All patches submitted must contain
a 'Signed-off-by' line from the author. Patches should follow the
guidelines set out in the HACKING and CODING_STYLE files.
Additional information on submitting patches can be found online via
the QEMU website
https://qemu.org/Contribute/SubmitAPatch
https://qemu.org/Contribute/TrivialPatches
Bug reporting
=============
The QEMU project uses Launchpad as its primary upstream bug tracker. Bugs
found when running code built from QEMU git or upstream released sources
should be reported via:
https://bugs.launchpad.net/qemu/
If using QEMU via an operating system vendor pre-built binary package, it
is preferable to report bugs to the vendor's own bug tracker first. If
the bug is also known to affect latest upstream code, it can also be
reported via launchpad.
For additional information on bug reporting consult:
https://qemu.org/Contribute/ReportABug
Contact
=======
The QEMU community can be contacted in a number of ways, with the two
main methods being email and IRC
- qemu-devel@nongnu.org
https://lists.nongnu.org/mailman/listinfo/qemu-devel
- #qemu on irc.oftc.net
Information on additional methods of contacting the community can be
found online via the QEMU website:
https://qemu.org/Contribute/StartHere
-- End
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