On Wed, 30 Apr 2025 18:05:25 +0200
Laurent Vivier
While running piHole using podman, traffic can trigger the following assert:
ASSSERTION FAILED in flow_alloc (flow.c:521): flow->f.state == FLOW_STATE_FREE
Backtrace shows that this happens in flow_defer_handler():
#4 0x00005610d6f5b481 flow_alloc (passt + 0xb481) #5 0x00005610d6f74f86 udp_flow_from_sock (passt + 0x24f86) #6 0x00005610d6f737c3 udp_sock_fwd (passt + 0x237c3) #7 0x00005610d6f74c07 udp_flush_flow (passt + 0x24c07) #8 0x00005610d6f752c2 udp_flow_defer (passt + 0x252c2) #9 0x00005610d6f5bce1 flow_defer_handler (passt + 0xbce1)
We are trying to allocate a new flow inside the loop freeing them.
Inside the loop free_head points to the first free flow entry in the current cluster. But if we allocate a new entry during the loop, free_head is not updated and can point now to the entry we have just allocated.
We can fix the problem by spliting the loop in two parts: - first part where we can close some of them and allocate some new flow entries, - second part where we free the entries closed in the previous loop and we aggregate the free entries to merge consecutive the clusters.
Link: https://github.com/containers/podman/issues/25959 Signed-off-by: Laurent Vivier
Applied, thanks! -- Stefano