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hw/virtio: fix crash in processing balloon stats 

balloon_stats_get_all will iterate over guest stats upto the max
VIRTIO_BALLOON_S_NR value, calling visit_type_uint64 to populate
the QObject dict. The dict keys are obtained from the static
array balloon_stat_names which is VIRTIO_BALLOON_S_NR in size.

Unfortunately the way that array is declared results in any
unassigned stats getting a NULL name, which will then cause
visit_type_uint64 to trigger an assert in qobject_output_add_obj.

The balloon_stat_names array was fortunately fully populated with
names until recently:

  commit 0d2eeef77a
  Author: Bibo Mao <maobibo@loongson.cn>
  Date:   Mon Oct 28 10:38:09 2024 +0800

    linux-headers: Update to Linux v6.12-rc5

pulled a change to include/standard-headers/linux/virtio_balloon.h
which increased VIRTIO_BALLOON_S_NR by 6, and failed to add the new
names to balloon_stat_names.

This commit fills in the missing names, and uses a static assert to
guarantee that any future changes to VIRTIO_BALLOON_S_NR will cause
a build failure until balloon_stat_names is updated.

This problem was detected by the Cockpit Project's automated
integration tests on QEMU 9.2.0-rc1.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2329448
Fixes: 0d2eeef77a ("linux-headers: Update to Linux v6.12-rc5")
Reported-by: Martin Pitt <mpitt@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20241129135507.699030-2-berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
This commit is contained in:
Daniel P. Berrangé 2024-11-29 13:55:05 +00:00 committed by Philippe Mathieu-Daudé
parent 302075f85e
commit bff1050a56
1 changed files with 15 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
hw/virtio/virtio-balloon.c
View File

@ -167,19 +167,33 @@ static void balloon_deflate_page(VirtIOBalloon *balloon,
}
}
/*
* All stats upto VIRTIO_BALLOON_S_NR /must/ have a
* non-NULL name declared here, since these are used
* as keys for populating the QDict with stats
*/
static const char *balloon_stat_names[] = {
[VIRTIO_BALLOON_S_SWAP_IN] = "stat-swap-in",
[VIRTIO_BALLOON_S_SWAP_OUT] = "stat-swap-out",
[VIRTIO_BALLOON_S_MAJFLT] = "stat-major-faults",
[VIRTIO_BALLOON_S_MINFLT] = "stat-minor-faults",
[VIRTIO_BALLOON_S_MEMFREE] = "stat-free-memory",
[VIRTIO_BALLOON_S_MEMTOT] = "stat-total-memory",
[VIRTIO_BALLOON_S_AVAIL] = "stat-available-memory",
[VIRTIO_BALLOON_S_CACHES] = "stat-disk-caches",
[VIRTIO_BALLOON_S_HTLB_PGALLOC] = "stat-htlb-pgalloc",
[VIRTIO_BALLOON_S_HTLB_PGFAIL] = "stat-htlb-pgfail",
[VIRTIO_BALLOON_S_NR] = NULL
[VIRTIO_BALLOON_S_OOM_KILL] = "stat-oom-kills",
[VIRTIO_BALLOON_S_ALLOC_STALL] = "stat-alloc-stalls",
[VIRTIO_BALLOON_S_ASYNC_SCAN] = "stat-async-scans",
[VIRTIO_BALLOON_S_DIRECT_SCAN] = "stat-direct-scans",
[VIRTIO_BALLOON_S_ASYNC_RECLAIM] = "stat-async-reclaims",
[VIRTIO_BALLOON_S_DIRECT_RECLAIM] = "stat-direct-reclaims",
};
G_STATIC_ASSERT(G_N_ELEMENTS(balloon_stat_names) == VIRTIO_BALLOON_S_NR);
/*
* reset_stats - Mark all items in the stats array as unset