=================================
kzalloc()
->memset(object, 0, size)
smp_wmb()
vg->vlan_devices_arrays[pidx][vidx] = array;
==================================
Because __vlan_group_get_device() function depends on this order.
otherwise we may get a wrong address from the hardware cache on
another cpu.
So fix it by adding memory barrier instruction to ensure the order
of memory operations.
Signed-off-by: Di Zhu <zhudi21@huawei.com>
---
/* v1 */
Link: https://lore.kernel.org/netdev/0d7c26f933eb4a95a170f021020e722e@huawei.com/
/* v2 */
-linyunsheng <linyunsheng@huawei.com>
-update commit message
-add code comments
---
net/8021q/vlan.c | 3 +++
net/8021q/vlan.h | 4 ++++
2 files changed, 7 insertions(+)
@@ -71,6 +71,9 @@ static int vlan_group_prealloc_vid(struct vlan_group *vg,
if (array == NULL)
return -ENOBUFS;
+ /* paired with smp_rmb() in __vlan_group_get_device() */
+ smp_wmb();
+
vg->vlan_devices_arrays[pidx][vidx] = array;
return 0;
}
@@ -57,6 +57,10 @@ static inline struct net_device *__vlan_group_get_device(struct vlan_group *vg,
array = vg->vlan_devices_arrays[pidx]
[vlan_id / VLAN_GROUP_ARRAY_PART_LEN];
+
+ /* paired with smp_wmb() in vlan_group_prealloc_vid() */
+ smp_rmb();
+
return array ? array[vlan_id % VLAN_GROUP_ARRAY_PART_LEN] : NULL;
}
From: Di Zhu <zhudi21@huawei.com> We encountered a crash: in the packet receiving process, we got an illegal VLAN device address, but the VLAN device address saved in vmcore is correct. After checking the code, we found a possible data competition: CPU 0: CPU 1: (RCU read lock) (RTNL lock) vlan_do_receive() register_vlan_dev() vlan_find_dev() ->__vlan_group_get_device() ->vlan_group_prealloc_vid() In vlan_group_prealloc_vid(), We need to make sure that memset() in kzalloc() is executed before assigning value to vlan devices array: