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---
ibmveth: Fix MQ RX poll and shutdown hangs after queue resize
This changes ibmveth_poll() to skip RX slots whose correlator cannot be
mapped to a buffer pool instead of retrying them forever, completes NAPI
when the interface is going down, and adds a descriptor length check
before skb_put(). The WARN_ON plus adapter reset escalation in the
correlator validation paths is replaced by a rate-limited message.
No Link: tags present in the commit header.
A few questions below.
[Severity: Low]
Would it make sense to split this into separate patches with individual
Fixes: tags? There appear to be four independent changes here:
- skipping bad RX correlators and dropping the WARN_ON/reset escalation
- completing NAPI when the interface is down or napi_disable is pending
- validating the descriptor length against skb tailroom before skb_put()
- changing the return value on the budget-exhausted shutdown path
There is no Fixes: tag, so stable maintainers cannot pick up the hang fix
without also picking up the policy change that removes the reset based
recovery, and the skb_put() hardening is not visible as a fix on its own.
> diff --git a/drivers/net/ethernet/ibm/ibmveth.c
> b/drivers/net/ethernet/ibm/ibmveth.c
> index c99d8e8be7b37..09e06d86701a5 100644
> --- a/drivers/net/ethernet/ibm/ibmveth.c
> +++ b/drivers/net/ethernet/ibm/ibmveth.c
> @@ -1376,6 +1376,24 @@ ibmveth_free_single_rx_queue(struct ibmveth_adapter
> *adapter, int queue_idx)
> netdev_dbg(adapter->netdev, "Freed queue %d resources\n", queue_idx);
> }
>
> +static bool ibmveth_rxq_correlator_valid(struct ibmveth_adapter *adapter,
> + int queue_index, u64 correlator)
> +{
> + unsigned int pool = correlator >> 32;
> + unsigned int index = correlator & 0xffffffffUL;
> +
> + return pool < IBMVETH_NUM_BUFF_POOLS &&
> + index < adapter->rx_buff_pool[queue_index][pool].size;
> +}
[Severity: High]
This isn't a bug introduced by this patch, since the pre-existing WARN_ON
checks were also bounds-only, but can a correlator naming an inactive or
already freed pool still pass ibmveth_rxq_correlator_valid() and then
dereference a NULL array?
ibmveth_init_buffer_pool() sets pool->size for all pools regardless of
active state, while ibmveth_alloc_queue_buffer_pools() skips inactive
pools, and ibmveth_free_buffer_pool() clears the arrays without clearing
size or active:
kfree(pool->free_map);
pool->free_map = NULL;
...
if (pool->skbuff) {
kfree(pool->skbuff);
pool->skbuff = NULL;
}
With the defaults in ibmveth.h:
static int pool_count[] = { 256, 512, 256, 256, 256 };
static int pool_active[] = { 1, 1, 0, 0, 0};
a correlator of pool=2, index=0 satisfies both conditions of the new
helper, and both users then index a NULL pointer before the !skb test can
help:
return adapter->rx_buff_pool[queue_index][pool].skbuff[index];
and
skb = adapter->rx_buff_pool[queue_index][pool].skbuff[index];
Should the helper also require pool->active and non-NULL skbuff/dma_addr/
free_map, or should ibmveth_free_buffer_pool() clear pool->size? The same
window seems to apply to pools torn down by ethtool -L scale-down, an MTU
change, or sysfs deactivation.
[Severity: Low]
This is a pre-existing weakness rather than something new here, but the
helper only bounds-checks, so a stale correlator that happens to land in
range after an ethtool -L resize is treated as a live frame. With
reuse=false the buffer can be handed to the stack while the hypervisor may
still own it, and with reuse=true the index is pushed onto free_map a
second time. Is there any generation counter or per-queue tag available in
the correlator that could distinguish a stale descriptor from a current
one?
> +
> +static void ibmveth_rxq_advance(struct ibmveth_rx_q *rxq)
> +{
> + if (++rxq->index == rxq->num_slots) {
> + rxq->index = 0;
> + rxq->toggle = !rxq->toggle;
> + }
> +}
> +
> /**
> * ibmveth_remove_buffer_from_pool - remove a buffer from a pool
> * @adapter: adapter instance
> @@ -1397,17 +1415,12 @@ static int ibmveth_remove_buffer_from_pool(struct
> ibmveth_adapter *adapter,
> unsigned int free_index;
> struct sk_buff *skb;
>
> - if (WARN_ON(pool >= IBMVETH_NUM_BUFF_POOLS) ||
> - WARN_ON(index >= adapter->rx_buff_pool[queue_index][pool].size)) {
> - schedule_work(&adapter->work);
> + if (!ibmveth_rxq_correlator_valid(adapter, queue_index, correlator))
> return -EINVAL;
> - }
>
> skb = adapter->rx_buff_pool[queue_index][pool].skbuff[index];
> - if (WARN_ON(!skb)) {
> - schedule_work(&adapter->work);
> + if (!skb)
> return -EFAULT;
> - }
[Severity: Medium]
The schedule_work(&adapter->work) escalation is dropped here and in
ibmveth_rxq_get_buffer(), so nothing bounds the condition any more. The
commit message describes the new skip policy but does not mention that all
recovery escalation is gone.
The previous reset performed a close/open cycle, which issued
h_free_logical_lan and re-registered the logical LAN, flushing every buffer
registration the hypervisor still held. If the bad correlator exists
because PHYP still holds buffers from a pool that
ibmveth_free_buffer_pool() already unmapped and freed during an
ethtool -L resize:
dma_unmap_single(&adapter->vdev->dev, pool->dma_addr[i],
pool->buff_size, DMA_FROM_DEVICE);
dev_kfree_skb_any(skb);
can the hypervisor keep writing into those freed pages indefinitely now
that the driver only logs and advances?
Separately, this also folds together two different classes: -EINVAL for an
out-of-range correlator, and -EFAULT where pool and index are in range but
skbuff[index] is NULL, which indicates driver/hypervisor state desync. Is
silently skipping the -EFAULT case intended?
And if the descriptor's correlator belongs to a different queue's pool, the
skip never reclaims that queue's slot, so that pool's available count stays
inflated and ibmveth_replenish_task() stops replenishing it:
if (pool->active && pool->free_map &&
(atomic_read(&pool->available) < pool->threshold))
>
> /* if we are going to reuse the buffer then keep the pointers around
> * but mark index as available. replenish will see the skb pointer and
> @@ -1452,11 +1465,8 @@ ibmveth_rxq_get_buffer(struct ibmveth_adapter *adapter,
> unsigned int pool = correlator >> 32;
> unsigned int index = correlator & 0xffffffffUL;
>
> - if (WARN_ON(pool >= IBMVETH_NUM_BUFF_POOLS) ||
> - WARN_ON(index >= adapter->rx_buff_pool[queue_index][pool].size)) {
> - schedule_work(&adapter->work);
> + if (!ibmveth_rxq_correlator_valid(adapter, queue_index, correlator))
> return NULL;
> - }
>
> return adapter->rx_buff_pool[queue_index][pool].skbuff[index];
> }
> @@ -1483,14 +1493,15 @@ static int ibmveth_rxq_harvest_buffer(struct
> ibmveth_adapter *adapter,
>
> cor = rxq->queue_addr[rxq->index].correlator;
> rc = ibmveth_remove_buffer_from_pool(adapter, cor, queue_index, reuse);
> - if (unlikely(rc))
> + if (unlikely(rc)) {
> + if (rc == -EINVAL || rc == -EFAULT)
> + goto advance;
> return rc;
> -
> - if (++rxq->index == rxq->num_slots) {
> - rxq->index = 0;
> - rxq->toggle = !rxq->toggle;
> }
>
> +advance:
> + ibmveth_rxq_advance(rxq);
> +
> return 0;
> }
[Severity: Low]
Can ibmveth_rxq_harvest_buffer() still return non-zero after this change?
ibmveth_remove_buffer_from_pool() has exactly three returns: -EINVAL,
-EFAULT and 0, and both error codes now go to the advance label, so
"return rc;" looks unreachable.
That would make all five "if (unlikely(rc)) break;" checks in
ibmveth_poll(), including the two added by this patch, dead code, along
with the harvest failure path in ibmveth_drain_rx_queue():
rc = ibmveth_rxq_harvest_buffer(adapter, queue_index, true);
if (rc) {
netdev_err(netdev,
"Failed to harvest buffer from queue %d during
drain: %d\n",
queue_index, rc);
break;
}
drained++;
Should unmappable slots encountered during drain still be counted as
drained++ with no diagnostic? The kernel-doc above harvest still documents
"other - non-zero return from ibmveth_remove_buffer_from_pool", which no
longer matches the implementation.
>
> @@ -3092,11 +3103,19 @@ static int ibmveth_poll(struct napi_struct *napi, int
> budget)
> if (WARN_ON(queue_index < 0 || queue_index >= adapter->num_rx_queues))
> return 0;
>
> + if (!netif_running(netdev) || napi_disable_pending(napi)) {
> + napi_complete_done(napi, 0);
> + return 0;
> + }
> +
> if (adapter->rx_qstats)
> adapter->rx_qstats[queue_index].polls++;
>
> restart_poll:
> while (frames_processed < budget) {
> + if (!netif_running(netdev) || napi_disable_pending(napi))
> + break;
> +
> if (!ibmveth_rxq_pending_buffer(adapter, queue_index))
> break;
>
[ ... ]
> @@ -3126,8 +3145,45 @@ static int ibmveth_poll(struct napi_struct *napi, int
> budget)
> __sum16 iph_check = 0;
>
> skb = ibmveth_rxq_get_buffer(adapter, queue_index);
> - if (unlikely(!skb))
> - break;
> + if (unlikely(!skb)) {
> + if (net_ratelimit())
> + netdev_err(netdev,
> + "bad correlator on queue %d,
> skipping slot\n",
> + queue_index);
[ ... ]
> +
> + if (unlikely((unsigned int)offset +
> + (unsigned int)length >
> + skb_tailroom(skb))) {
[Severity: High]
This is not a regression from this patch, since there was no length check
at all before, but can this check be bypassed by 32-bit wraparound?
Both operands are cast to unsigned int, so the sum is modulo 2^32. Unlike
offset, length is not masked; ibmveth_rxq_frame_length() returns the whole
descriptor field:
return be32_to_cpu(rxq->queue_addr[rxq->index].length);
and in ibmveth.h that field is a full __be32 written by the hypervisor,
while only offset gets IBMVETH_RXQ_OFF_MASK (0x0000FFFF).
For a corrupted length like 0xFFFFFFF0 with a small offset, the addition
wraps to a small value and the guard does not fire. The copybreak test
compares against "static unsigned int rx_copybreak", so 0xFFFFFFF0 is not
less than rx_copybreak and no copy skb is allocated, and execution reaches:
skb_put(skb, length);
which trips skb_over_panic() -> BUG(). Would an overflow-safe form work
better here, for example:
if (offset > tailroom || length > tailroom - offset)
or validating length against pool->buff_size?
[ ... ]
> @@ -3206,8 +3262,14 @@ static int ibmveth_poll(struct napi_struct *napi, int
> budget)
>
> ibmveth_replenish_task(adapter, queue_index);
>
> - if (frames_processed == budget)
> + if (frames_processed == budget) {
> + if (!netif_running(netdev) || napi_disable_pending(napi)) {
> + napi_complete_done(napi, frames_processed);
> + /* After complete_done, must not return full budget. */
> + return frames_processed ? frames_processed - 1 : 0;
> + }
> goto out;
> + }
>
> if (!napi_complete_done(napi, frames_processed))
> goto out;
> @@ -3225,6 +3287,8 @@ static int ibmveth_poll(struct napi_struct *napi, int
> budget)
> }
>
> if (ibmveth_rxq_pending_buffer(adapter, queue_index) &&
> + netif_running(netdev) &&
> + !napi_disable_pending(napi) &&
> napi_schedule(napi)) {
> lpar_rc = ibmveth_disable_irq(adapter, queue_index);
> WARN_ON(lpar_rc != H_SUCCESS);
[Severity: High]
This isn't a bug introduced by this patch, as the
napi_complete_done() -> ibmveth_enable_irq() -> ibmveth_rxq_pending_buffer()
sequence is unchanged, but do the new guards actually close the shutdown
window the commit message describes?
The new mid-loop break also lands here with frames_processed < budget, so
the quiesce case still reaches:
if (!napi_complete_done(napi, frames_processed))
goto out;
Clearing NAPI_STATE_SCHED there is what napi_disable() waits for, so
ibmveth_close() can proceed past ibmveth_cleanup_rx_interrupts() into
ibmveth_cleanup_rx_resources():
if (adapter->rx_queue[i].queue_addr) {
dma_free_coherent(dev, adapter->rx_queue[i].queue_len,
adapter->rx_queue[i].queue_addr,
adapter->rx_queue[i].queue_dma);
adapter->rx_queue[i].queue_addr = NULL;
while the still running poll executes:
lpar_rc = ibmveth_enable_irq(adapter, queue_index);
re-arming the PHYP interrupt that close just masked, and then evaluates
ibmveth_rxq_pending_buffer(), which reads
rxq->queue_addr[rxq->index].flags_off - a NULL dereference or a read of
freed coherent memory. ibmveth_close() has no synchronize_net() between
napi_disable()/free_irq() and the frees, unlike the scale-down path.
Note the new netif_running()/napi_disable_pending() terms are evaluated
after ibmveth_rxq_pending_buffer() in the same condition, so they cannot
prevent that access; they only suppress the following
ibmveth_disable_irq().
Related question on that suppression: in the window where
__LINK_STATE_START is already cleared by __dev_close_many() but
NAPI_STATE_DISABLE is not yet set, the pre-patch code re-masked PHYP via
the napi_schedule() branch. With the new guards, poll now returns leaving
delivery unmasked into the napi_disable()/free_irq() window, and the
interrupt handler does not mask either when napi_schedule_prep() fails:
if (napi_schedule_prep(napi)) {
lpar_rc = ibmveth_disable_irq(adapter, qindex);
WARN_ON(lpar_rc != H_SUCCESS);
__napi_schedule(napi);
}
Can that leave the queue interrupt storming until free_irq()?
[ ... ]
