37035df51e
Since commit 61f20b9dc5b7 ("spapr_nvram: Pre-initialize the NVRAM to
support the -prom-env parameter"), pseries machines can pre-initialize
the "system" partition in the NVRAM with the data passed to all -prom-env
parameters on the QEMU command line.
In this case it is assumed that all the data fits in 64 KiB, but the user
can easily pass more and crash QEMU:
$ qemu-system-ppc64 -M pseries $(for ((x=0;x<128;x++)); do \
echo -n " -prom-env " ; printf "%0.sx" {1..1024}; \
done) # this requires ~128 Kib
malloc(): corrupted top size
Aborted (core dumped)
This happens because we don't check if all the prom-env data fits in
the NVRAM and chrp_nvram_set_var() happily memcpy() it passed the
buffer.
This crash affects basically all ppc/ppc64 machine types that use -prom-env:
- pseries (all versions)
- g3beige
- mac99
and also sparc/sparc64 machine types:
- LX
- SPARCClassic
- SPARCbook
- SS-10
- SS-20
- SS-4
- SS-5
- SS-600MP
- Voyager
- sun4u
- sun4v
Add a max_len argument to chrp_nvram_create_system_partition() so that
it can check the available size before writing to memory.
Since NVRAM is populated at machine init, it seems reasonable to consider
this error as fatal. So, instead of reporting an error when we detect that
the NVRAM is too small and adapt all machine types to handle it, we simply
exit QEMU in all cases. This is still better than crashing. If someone
wants another behavior, I guess this can be reworked later.
Tested with:
$ yes q | \
(for arch in ppc ppc64 sparc sparc64; do \
echo == $arch ==; \
qemu=${arch}-softmmu/qemu-system-$arch; \
for mach in $($qemu -M help | awk '! /^Supported/ { print $1 }'); do \
echo $mach; \
$qemu -M $mach -monitor stdio -nodefaults -nographic \
$(for ((x=0;x<128;x++)); do \
echo -n " -prom-env " ; printf "%0.sx" {1..1024}; \
done) >/dev/null; \
done; echo; \
done)
Without the patch, affected machine types cause QEMU to report some
memory corruption and crash:
malloc(): corrupted top size
free(): invalid size
*** stack smashing detected ***: terminated
With the patch, QEMU prints the following message and exits:
NVRAM is too small. Try to pass less data to -prom-env
It seems that the conditions for the crash have always existed, but it
affects pseries, the machine type I care for, since commit 61f20b9dc5b7
only.
Fixes: 61f20b9dc5b7 ("spapr_nvram: Pre-initialize the NVRAM to support the -prom-env parameter")
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1867739
Reported-by: John Snow <jsnow@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <159736033937.350502.12402444542194031035.stgit@bahia.lan>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
=========== 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: .. code-block:: shell 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. .. code-block:: shell git clone https://git.qemu.org/git/qemu.git When submitting patches, one common 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 CODING_STYLE.rst file. Additional information on submitting patches can be found online via the QEMU website * `<https://qemu.org/Contribute/SubmitAPatch>`_ * `<https://qemu.org/Contribute/TrivialPatches>`_ The QEMU website is also maintained under source control. .. code-block:: shell git clone https://git.qemu.org/git/qemu-web.git * `<https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/>`_ A 'git-publish' utility was created to make above process less cumbersome, and is highly recommended for making regular contributions, or even just for sending consecutive patch series revisions. It also requires a working 'git send-email' setup, and by default doesn't automate everything, so you may want to go through the above steps manually for once. For installation instructions, please go to * `<https://github.com/stefanha/git-publish>`_ The workflow with 'git-publish' is: .. code-block:: shell $ git checkout master -b my-feature $ # work on new commits, add your 'Signed-off-by' lines to each $ git publish Your patch series will be sent and tagged as my-feature-v1 if you need to refer back to it in the future. Sending v2: .. code-block:: shell $ git checkout my-feature # same topic branch $ # making changes to the commits (using 'git rebase', for example) $ git publish Your patch series will be sent with 'v2' tag in the subject and the git tip will be tagged as my-feature-v2. 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 * `<mailto: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>`_