When a bound net_device is unregistered while userspace still holds a
netlink or TCP socket reference on a devmem binding,
mp_dmabuf_devmem_uninstall() clears binding->dev to NULL so
netdev_nl_sock_priv_destroy() will not touch the unregistered
net_device, but leaves the dma_buf attachment mapped until
__net_devmem_dmabuf_binding_free() runs later on socket close.
Because dma_buf_attach() does not take a reference on dma_dev, device
removal frees dma_dev while the attachment is still mapped. Closing the
netlink socket afterwards triggers a slab use-after-free in
dma_unmap_sg_attrs():
BUG: KASAN: slab-use-after-free in dma_unmap_sg_attrs+0x76/0x2b0
Read of size 8 at addr ffff88810fae64b0 by task kworker/3:1/53
Workqueue: events __net_devmem_dmabuf_binding_free
Call Trace:
dma_unmap_sg_attrs+0x76/0x2b0
unmap_udmabuf+0x8e/0x100
dma_buf_unmap_attachment+0x145/0x330
dma_buf_unmap_attachment_unlocked+0x96/0x130
__net_devmem_dmabuf_binding_free+0x156/0x2e0
Freed by task 9:
kfree+0x1b8/0x550
nsim_bus_dev_release+0xe/0x60
device_release+0xcf/0x250
Add net_devmem_dmabuf_binding_unmap() serialized under binding->lock
and null out binding->sgt and binding->attachment after unmapping so
unmapping is idempotent across queue uninstall and deferred binding
destruction. Call it synchronously when the last bound RX queue is
uninstalled in mp_dmabuf_devmem_uninstall().
Fixes: f8350a4358fc ("net: page_pool: add a mp hook to unregister_netdevice*")
Fixes: 0afc44d8cdf6 ("net: devmem: fix kernel panic when netlink socket close
after module unload")
Cc: Taehee Yoo <[email protected]>
Cc: Stanislav Fomichev <[email protected]>
Cc: Tariq Toukan <[email protected]>
Cc: Kaifeng Wang <[email protected]>
Signed-off-by: Mina Almasry <[email protected]>
---
net/core/devmem.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/net/core/devmem.c b/net/core/devmem.c
index f4d60654ce7fd..5e4070b82df44 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -58,6 +58,21 @@ static void net_devmem_dmabuf_binding_release(struct
percpu_ref *ref)
schedule_work(&binding->unbind_w);
}
+static void
+net_devmem_dmabuf_binding_unmap(struct net_devmem_dmabuf_binding *binding)
+{
+ lockdep_assert_held(&binding->lock);
+
+ if (!binding->sgt)
+ return;
+
+ dma_buf_unmap_attachment_unlocked(binding->attachment, binding->sgt,
+ binding->direction);
+ dma_buf_detach(binding->dmabuf, binding->attachment);
+ binding->sgt = NULL;
+ binding->attachment = NULL;
+}
+
void __net_devmem_dmabuf_binding_free(struct work_struct *wq)
{
struct net_devmem_dmabuf_binding *binding = container_of(wq,
typeof(*binding), unbind_w);
@@ -74,9 +89,10 @@ void __net_devmem_dmabuf_binding_free(struct work_struct *wq)
size, avail))
gen_pool_destroy(binding->chunk_pool);
- dma_buf_unmap_attachment_unlocked(binding->attachment, binding->sgt,
- binding->direction);
- dma_buf_detach(binding->dmabuf, binding->attachment);
+ mutex_lock(&binding->lock);
+ net_devmem_dmabuf_binding_unmap(binding);
+ mutex_unlock(&binding->lock);
+
dma_buf_put(binding->dmabuf);
xa_destroy(&binding->bound_rxqs);
percpu_ref_exit(&binding->ref);
@@ -535,6 +551,7 @@ static void mp_dmabuf_devmem_uninstall(void *mp_priv,
mutex_lock(&binding->lock);
ASSERT_EXCLUSIVE_WRITER(binding->dev);
WRITE_ONCE(binding->dev, NULL);
+ net_devmem_dmabuf_binding_unmap(binding);
mutex_unlock(&binding->lock);
}
break;
--
2.56.0.385.gd3acb90ef8-goog
