TX devmem bindings (NETDEV_CMD_BIND_TX) have no bound RX queues, so
mp_dmabuf_devmem_uninstall() never runs when binding->dev or
binding->vdev unregisters. As a result, binding->dev and binding->vdev
dangle pointing to freed struct net_device memory, and the dma_buf
remains attached and mapped after device removal.
Closing the netlink socket after netdev unregistration dereferences the
freed struct net_device in netdev_nl_sock_priv_destroy():
BUG: unable to handle page fault for address: ffff88824ca9b000
Oops: Oops: 0000 [#1] SMP KASAN NOPTI
RIP: 0010:netdev_nl_sock_priv_destroy+0xbd/0x1e0
Call Trace:
genl_release+0xf5/0x190
netlink_release+0xd01/0x18d0
__sock_release+0xb0/0x270
sock_close+0x18/0x20
Extend net_devmem_dev_unregister() to TX bindings, including ones
whose netlink socket is already closed but which TCP retransmits keep
alive:
- When binding->dev (the physical DMA-capable device) unregisters,
clear the binding's NET_DEVMEM_BINDING_LIVE mark and both
binding->dev and binding->vdev, and unmap the dma_buf under
binding->lock. No grace period is needed: the device is already
closed, so nothing hands the DMA addresses to the hardware anymore,
and concurrent senders only compare against binding->dev.
- When only binding->vdev (virtual device) unregisters while
binding->dev lives, only clear binding->vdev so no new TX sends match
the virtual device while allowing in-flight TX packets on binding->dev
to finish DMA safely.
Fixes: bd61848900bf ("net: devmem: Implement TX path")
Fixes: 1abe839b34ae ("net: devmem: support TX over NETMEM_TX_NO_DMA devices")
Suggested-by: Stanislav Fomichev <[email protected]>
Cc: Kaiyuan Zhang <[email protected]>
Cc: Bobby Eshleman <[email protected]>
Cc: Tariq Toukan <[email protected]>
Cc: Kaifeng Wang <[email protected]>
Assisted-by: LLM
Signed-off-by: Mina Almasry <[email protected]>
Reviewed-by: Dragos Tatulea <[email protected]>
---
v4:
- Detach and unmap TX bindings directly from the xarray walk, without a
grace period or a second pass (Stanislav).
v3:
- Detach all matching TX bindings first, then call synchronize_net()
once before unmapping them, instead of once per binding. Don't wait
for a grace period when only binding->vdev is cleared, since vdev is
never dereferenced (Sashiko).
- Don't detach TX bindings when the device only moves to another netns
(Sashiko).
v2:
- Build on the net_devmem_dev_unregister() walk from the previous patch,
so unbound TX bindings are also detached (Sashiko). Clear the
binding's LIVE mark instead of erasing its ID.
- The walk holds net_devmem_lock, which the final free also takes
before erasing the binding, instead of using RCU and
percpu_ref_tryget(), so it no longer takes a binding reference
(Stanislav).
---
net/core/devmem.c | 22 +++++++++++++++++++++-
net/core/devmem.h | 3 ++-
2 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/net/core/devmem.c b/net/core/devmem.c
index 20d95b24d5951..d33a092c6e4bb 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -207,11 +207,30 @@ net_devmem_dev_unregister_rx(struct
net_devmem_dmabuf_binding *binding,
NET_DEVMEM_BINDING_LIVE);
}
+static bool
+net_devmem_dev_unregister_tx(struct net_devmem_dmabuf_binding *binding,
+ unsigned long xa_idx, struct net_device *dev)
+{
+ if (binding->direction != DMA_TO_DEVICE)
+ return false;
+
+ if (READ_ONCE(binding->vdev) == dev)
+ WRITE_ONCE(binding->vdev, NULL);
+
+ if (READ_ONCE(binding->dev) != dev)
+ return false;
+
+ __xa_clear_mark(&net_devmem_dmabuf_bindings, xa_idx,
+ NET_DEVMEM_BINDING_LIVE);
+ return true;
+}
+
static void net_devmem_dev_detach(struct net_devmem_dmabuf_binding *binding,
struct net_device *dev)
{
mutex_lock(&binding->lock);
WRITE_ONCE(binding->dev, NULL);
+ WRITE_ONCE(binding->vdev, NULL);
if (!netif_is_queue_leasee(dev))
net_devmem_dmabuf_binding_unmap(binding);
mutex_unlock(&binding->lock);
@@ -229,7 +248,8 @@ void net_devmem_dev_unregister(struct net_device *dev)
xa_lock(&net_devmem_dmabuf_bindings);
xa_for_each(&net_devmem_dmabuf_bindings, xa_idx, binding) {
- if (!net_devmem_dev_unregister_rx(binding, xa_idx, dev))
+ if (!net_devmem_dev_unregister_rx(binding, xa_idx, dev) &&
+ !net_devmem_dev_unregister_tx(binding, xa_idx, dev))
continue;
xa_unlock(&net_devmem_dmabuf_bindings);
diff --git a/net/core/devmem.h b/net/core/devmem.h
index a834e0f698c7e..ce069e1736416 100644
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -39,7 +39,8 @@ struct net_devmem_dmabuf_binding {
* The binding undos itself and unmaps the underlying dmabuf once all
* those refs are dropped and the binding is no longer desired or in
* use. RX bindings are unmapped earlier, once they are no longer
- * installed on any queue.
+ * installed on any queue. TX bindings are unmapped earlier if their
+ * device is unregistered.
*
* net_devmem_get_net_iov() on dmabuf net_iovs will increment this
* reference, making sure that the binding remains alive until all the
--
2.56.0.176.g3575e65682-goog
