drivers/net/virtio_net.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-)
There is a bug when setting the RSS options in virtio_net that can break
the whole machine, getting the kernel into an infinite loop.
Running the following command in any QEMU virtual machine with virtionet
will reproduce this problem:
# ethtool -X eth0 hfunc toeplitz
This is how the problem happens:
1) ethtool_set_rxfh() calls virtnet_set_rxfh()
2) virtnet_set_rxfh() calls virtnet_commit_rss_command()
3) virtnet_commit_rss_command() populates 4 entries for the rss
scatter-gather
4) Since the command above does not have a key, then the last
scatter-gatter entry will be zeroed, since rss_key_size == 0.
sg_buf_size = vi->rss_key_size;
5) This buffer is passed to qemu, but qemu is not happy with a buffer
with zero length, and do the following in virtqueue_map_desc() (QEMU
function):
if (!sz) {
virtio_error(vdev, "virtio: zero sized buffers are not allowed");
6) virtio_error() (also QEMU function) set the device as broken
vdev->broken = true;
7) Qemu bails out, and do not repond this crazy kernel.
8) The kernel is waiting for the response to come back (function
virtnet_send_command())
9) The kernel is waiting doing the following :
while (!virtqueue_get_buf(vi->cvq, &tmp) &&
!virtqueue_is_broken(vi->cvq))
cpu_relax();
10) None of the following functions above is true, thus, the kernel
loops here forever. Keeping in mind that virtqueue_is_broken() does
not look at the qemu `vdev->broken`, so, it never realizes that the
vitio is broken at QEMU side.
Fix it by not sending RSS commands if the feature is not available in
the device.
Fixes: c7114b1249fa ("drivers/net/virtio_net: Added basic RSS support.")
Cc: stable@vger.kernel.org
Cc: qemu-devel@nongnu.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Heng Qi <hengqi@linux.alibaba.com>
---
Changelog:
V2:
* Moved from creating a valid packet, by rejecting the request
completely.
V3:
* Got some good feedback from and Xuan Zhuo and Heng Qi, and reworked
the rejection path.
V4:
* Added a comment in an "if" clause, as suggested by Michael S. Tsirkin.
---
drivers/net/virtio_net.c | 26 ++++++++++++++++++++++----
1 file changed, 22 insertions(+), 4 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c22d1118a133..115c3c5414f2 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3807,6 +3807,7 @@ static int virtnet_set_rxfh(struct net_device *dev,
struct netlink_ext_ack *extack)
{
struct virtnet_info *vi = netdev_priv(dev);
+ bool update = false;
int i;
if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE &&
@@ -3814,13 +3815,28 @@ static int virtnet_set_rxfh(struct net_device *dev,
return -EOPNOTSUPP;
if (rxfh->indir) {
+ if (!vi->has_rss)
+ return -EOPNOTSUPP;
+
for (i = 0; i < vi->rss_indir_table_size; ++i)
vi->ctrl->rss.indirection_table[i] = rxfh->indir[i];
+ update = true;
}
- if (rxfh->key)
+
+ if (rxfh->key) {
+ /* If either _F_HASH_REPORT or _F_RSS are negotiated, the
+ * device provides hash calculation capabilities, that is,
+ * hash_key is configured.
+ */
+ if (!vi->has_rss && !vi->has_rss_hash_report)
+ return -EOPNOTSUPP;
+
memcpy(vi->ctrl->rss.key, rxfh->key, vi->rss_key_size);
+ update = true;
+ }
- virtnet_commit_rss_command(vi);
+ if (update)
+ virtnet_commit_rss_command(vi);
return 0;
}
@@ -4729,13 +4745,15 @@ static int virtnet_probe(struct virtio_device *vdev)
if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
vi->has_rss_hash_report = true;
- if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS))
+ if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) {
vi->has_rss = true;
- if (vi->has_rss || vi->has_rss_hash_report) {
vi->rss_indir_table_size =
virtio_cread16(vdev, offsetof(struct virtio_net_config,
rss_max_indirection_table_length));
+ }
+
+ if (vi->has_rss || vi->has_rss_hash_report) {
vi->rss_key_size =
virtio_cread8(vdev, offsetof(struct virtio_net_config, rss_max_key_size));
--
2.43.0
Hello: This patch was applied to netdev/net.git (main) by David S. Miller <davem@davemloft.net>: On Wed, 3 Apr 2024 08:43:12 -0700 you wrote: > There is a bug when setting the RSS options in virtio_net that can break > the whole machine, getting the kernel into an infinite loop. > > Running the following command in any QEMU virtual machine with virtionet > will reproduce this problem: > > # ethtool -X eth0 hfunc toeplitz > > [...] Here is the summary with links: - [net,v4] virtio_net: Do not send RSS key if it is not supported https://git.kernel.org/netdev/net/c/059a49aa2e25 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
On Wed, 3 Apr 2024 08:43:12 -0700, Breno Leitao <leitao@debian.org> wrote: > There is a bug when setting the RSS options in virtio_net that can break > the whole machine, getting the kernel into an infinite loop. > > Running the following command in any QEMU virtual machine with virtionet > will reproduce this problem: > > # ethtool -X eth0 hfunc toeplitz > > This is how the problem happens: > > 1) ethtool_set_rxfh() calls virtnet_set_rxfh() > > 2) virtnet_set_rxfh() calls virtnet_commit_rss_command() > > 3) virtnet_commit_rss_command() populates 4 entries for the rss > scatter-gather > > 4) Since the command above does not have a key, then the last > scatter-gatter entry will be zeroed, since rss_key_size == 0. > sg_buf_size = vi->rss_key_size; > > 5) This buffer is passed to qemu, but qemu is not happy with a buffer > with zero length, and do the following in virtqueue_map_desc() (QEMU > function): > > if (!sz) { > virtio_error(vdev, "virtio: zero sized buffers are not allowed"); > > 6) virtio_error() (also QEMU function) set the device as broken > > vdev->broken = true; > > 7) Qemu bails out, and do not repond this crazy kernel. > > 8) The kernel is waiting for the response to come back (function > virtnet_send_command()) > > 9) The kernel is waiting doing the following : > > while (!virtqueue_get_buf(vi->cvq, &tmp) && > !virtqueue_is_broken(vi->cvq)) > cpu_relax(); > > 10) None of the following functions above is true, thus, the kernel > loops here forever. Keeping in mind that virtqueue_is_broken() does > not look at the qemu `vdev->broken`, so, it never realizes that the > vitio is broken at QEMU side. > > Fix it by not sending RSS commands if the feature is not available in > the device. > > Fixes: c7114b1249fa ("drivers/net/virtio_net: Added basic RSS support.") > Cc: stable@vger.kernel.org > Cc: qemu-devel@nongnu.org > Signed-off-by: Breno Leitao <leitao@debian.org> > Reviewed-by: Heng Qi <hengqi@linux.alibaba.com> Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > --- > Changelog: > > V2: > * Moved from creating a valid packet, by rejecting the request > completely. > V3: > * Got some good feedback from and Xuan Zhuo and Heng Qi, and reworked > the rejection path. > V4: > * Added a comment in an "if" clause, as suggested by Michael S. Tsirkin. > > --- > drivers/net/virtio_net.c | 26 ++++++++++++++++++++++---- > 1 file changed, 22 insertions(+), 4 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index c22d1118a133..115c3c5414f2 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -3807,6 +3807,7 @@ static int virtnet_set_rxfh(struct net_device *dev, > struct netlink_ext_ack *extack) > { > struct virtnet_info *vi = netdev_priv(dev); > + bool update = false; > int i; > > if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE && > @@ -3814,13 +3815,28 @@ static int virtnet_set_rxfh(struct net_device *dev, > return -EOPNOTSUPP; > > if (rxfh->indir) { > + if (!vi->has_rss) > + return -EOPNOTSUPP; > + > for (i = 0; i < vi->rss_indir_table_size; ++i) > vi->ctrl->rss.indirection_table[i] = rxfh->indir[i]; > + update = true; > } > - if (rxfh->key) > + > + if (rxfh->key) { > + /* If either _F_HASH_REPORT or _F_RSS are negotiated, the > + * device provides hash calculation capabilities, that is, > + * hash_key is configured. > + */ > + if (!vi->has_rss && !vi->has_rss_hash_report) > + return -EOPNOTSUPP; > + > memcpy(vi->ctrl->rss.key, rxfh->key, vi->rss_key_size); > + update = true; > + } > > - virtnet_commit_rss_command(vi); > + if (update) > + virtnet_commit_rss_command(vi); > > return 0; > } > @@ -4729,13 +4745,15 @@ static int virtnet_probe(struct virtio_device *vdev) > if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT)) > vi->has_rss_hash_report = true; > > - if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) > + if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) { > vi->has_rss = true; > > - if (vi->has_rss || vi->has_rss_hash_report) { > vi->rss_indir_table_size = > virtio_cread16(vdev, offsetof(struct virtio_net_config, > rss_max_indirection_table_length)); > + } > + > + if (vi->has_rss || vi->has_rss_hash_report) { > vi->rss_key_size = > virtio_cread8(vdev, offsetof(struct virtio_net_config, rss_max_key_size)); > > -- > 2.43.0 >
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