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ba4ba11ed6
tbl_mask_array_realloc() retires the old mask_array before it stops being
reachable:
old = ovsl_dereference(tbl->mask_array);
if (old) {
...
call_rcu(&old->rcu, mask_array_rcu_cb);
}
rcu_assign_pointer(tbl->mask_array, new);
call_rcu() only waits for read-side critical sections already in flight.
tbl->mask_array still points at old between the call_rcu() and the
rcu_assign_pointer(), so a reader entering ovs_flow_tbl_lookup_stats() in
that window picks up old in a fresh critical section that the pending
grace period does not cover.
tbl_mask_array_realloc() runs in process context under ovs_mutex, so the
window is preemptible and can outlast the grace period. Then
mask_array_rcu_cb() frees old before the swap runs:
BUG: KASAN: slab-use-after-free in flow_lookup.constprop.0+0x2bf/0x2f0
Read of size 8 at addr ffff888020b3e018 by task poc/741
flow_lookup.constprop.0+0x2bf/0x2f0
ovs_flow_tbl_lookup_stats+0x4a3/0x5c0
ovs_dp_process_packet+0x19c/0x710
ovs_vport_receive+0x243/0x390
internal_dev_xmit+0x81/0x170
Freed by task 728:
kfree+0x16a/0x4e0
rcu_core+0x853/0x1030
Publish the new array before retiring the old one. The kfree_rcu() that
call_rcu() replaced ran after the swap.
Fixes:
|
||
|---|---|---|
| .. | ||
| actions.c | ||
| conntrack.c | ||
| conntrack.h | ||
| datapath.c | ||
| datapath.h | ||
| dp_notify.c | ||
| drop.h | ||
| flow_netlink.c | ||
| flow_netlink.h | ||
| flow_table.c | ||
| flow_table.h | ||
| flow.c | ||
| flow.h | ||
| Kconfig | ||
| Makefile | ||
| meter.c | ||
| meter.h | ||
| openvswitch_trace.c | ||
| openvswitch_trace.h | ||
| vport-internal_dev.c | ||
| vport-internal_dev.h | ||
| vport-netdev.c | ||
| vport-netdev.h | ||
| vport.c | ||
| vport.h | ||