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[AUTOSEL,for,4.9,060/100] virtio_balloon: prevent uninitialized variable use

Message ID 20171213015722.6722-35-alexander.levin@verizon.com
State New
Headers show
Series None | expand

Commit Message

Levin, Alexander (Sasha Levin) Dec. 13, 2017, 1:57 a.m. UTC 
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>

---
 drivers/virtio/virtio_balloon.c | 2 ++
 1 file changed, 2 insertions(+)

-- 
2.11.0
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Patch

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 07b07b12ef90..a7c08cc4c1b7 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -253,12 +253,14 @@  static unsigned int update_balloon_stats(struct virtio_balloon *vb)
 
 	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,