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hw/net: Fix NULL dereference with software RSS

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When an eBPF program cannot be attached, virtio_net_load_ebpf() returns
false, and virtio_net_device_realize() enters the code path to handle
errors because of this, but it causes NULL dereference because no error
is generated.

Change virtio_net_load_ebpf() to return false only when a fatal error
occurred.

Fixes: b5900dff14 ("hw/net: report errors from failing to use eBPF RSS FDs")
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-Id: <20250116-software-v1-1-9e5161b534d8@daynix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Akihiko Odaki 2025-01-16 16:30:43 +09:00 • committed by Michael S. Tsirkin
parent 6f9a1a0143
commit bc82af6b0d
1 changed files with 18 additions and 27 deletions
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45
hw/net/virtio-net.c
View file

@ -1352,18 +1352,25 @@ exit:
static bool virtio_net_load_ebpf(VirtIONet *n, Error **errp)
{
bool ret = false;
if (virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
trace_virtio_net_rss_load(n, n->nr_ebpf_rss_fds, n->ebpf_rss_fds);
if (n->ebpf_rss_fds) {
ret = virtio_net_load_ebpf_fds(n, errp);
} else {
ret = ebpf_rss_load(&n->ebpf_rss, errp);
}
if (!virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
return true;
}
return ret;
trace_virtio_net_rss_load(n, n->nr_ebpf_rss_fds, n->ebpf_rss_fds);
/*
* If user explicitly gave QEMU RSS FDs to use, then
* failing to use them must be considered a fatal
* error. If no RSS FDs were provided, QEMU is trying
* eBPF on a "best effort" basis only, so report a
* warning and allow fallback to software RSS.
*/
if (n->ebpf_rss_fds) {
return virtio_net_load_ebpf_fds(n, errp);
}
ebpf_rss_load(&n->ebpf_rss, &error_warn);
return true;
}
static void virtio_net_unload_ebpf(VirtIONet *n)
@ -3913,23 +3920,7 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
net_rx_pkt_init(&n->rx_pkt);
if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS)) {
Error *err = NULL;
if (!virtio_net_load_ebpf(n, &err)) {
/*
* If user explicitly gave QEMU RSS FDs to use, then
* failing to use them must be considered a fatal
* error. If no RSS FDs were provided, QEMU is trying
* eBPF on a "best effort" basis only, so report a
* warning and allow fallback to software RSS.
*/
if (n->ebpf_rss_fds) {
error_propagate(errp, err);
} else {
warn_report("unable to load eBPF RSS: %s",
error_get_pretty(err));
error_free(err);
}
}
virtio_net_load_ebpf(n, errp);
}
}