This is a note to let you know that I've just added the patch titled

virtio_balloon: prevent uninitialized variable use

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: virtio_balloon-prevent-uninitialized-variable-use.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Dec 21 09:02:40 CET 2017

From: Arnd Bergmann arnd@arndb.de Date: Tue, 28 Mar 2017 18:46:59 +0200 Subject: virtio_balloon: prevent uninitialized variable use

From: Arnd Bergmann arnd@arndb.de

[ Upstream commit f0bb2d50dfcc519f06f901aac88502be6ff1df2c ]

The latest gcc-7.0.1 snapshot reports a new warning:

virtio/virtio_balloon.c: In function 'update_balloon_stats': virtio/virtio_balloon.c:258:26: error: 'events[2]' is used uninitialized in this function [-Werror=uninitialized] virtio/virtio_balloon.c:260:26: error: 'events[3]' is used uninitialized in this function [-Werror=uninitialized] virtio/virtio_balloon.c:261:56: error: 'events[18]' is used uninitialized in this function [-Werror=uninitialized] virtio/virtio_balloon.c:262:56: error: 'events[17]' is used uninitialized in this function [-Werror=uninitialized]

This seems absolutely right, so we should add an extra check to prevent copying uninitialized stack data into the statistics.

From all I can tell, this has been broken since the statistics code

was originally added in 2.6.34.

Fixes: 9564e138b1f6 ("virtio: Add memory statistics reporting to the balloon driver (V4)") Signed-off-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Ladi Prosek lprosek@redhat.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/virtio/virtio_balloon.c | 2 ++ 1 file changed, 2 insertions(+)

--- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -253,12 +253,14 @@ static unsigned int update_balloon_stats

available = si_mem_available();

+#ifdef CONFIG_VM_EVENT_COUNTERS update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, pages_to_bytes(events[PSWPIN])); update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, pages_to_bytes(events[PSWPOUT])); update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); +#endif update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, pages_to_bytes(i.freeram)); update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,

Patches currently in stable-queue which might be from arnd@arndb.de are

queue-4.9/hwmon-asus_atk0110-fix-uninitialized-data-access.patch queue-4.9/bna-avoid-writing-uninitialized-data-into-hw-registers.patch queue-4.9/virtio-balloon-use-actual-number-of-stats-for-stats-queue-buffers.patch queue-4.9/virtio_balloon-prevent-uninitialized-variable-use.patch queue-4.9/isdn-kcapi-avoid-uninitialized-data.patch