CVE-2023-53463

In the Linux kernel, the following vulnerability has been resolved:

ibmvnic: Do not reset dql stats on NON_FATAL err

All ibmvnic resets, make a call to netdev_tx_reset_queue() when

re-opening the device. netdev_tx_reset_queue() resets the num_queued

and num_completed byte counters. These stats are used in Byte Queue

Limit (BQL) algorithms. The difference between these two stats tracks

the number of bytes currently sitting on the physical NIC. ibmvnic

increases the number of queued bytes though calls to

netdev_tx_sent_queue() in the drivers xmit function. When, VIOS reports

that it is done transmitting bytes, the ibmvnic device increases the

number of completed bytes through calls to netdev_tx_completed_queue().

It is important to note that the driver batches its transmit calls and

num_queued is increased every time that an skb is added to the next

batch, not necessarily when the batch is sent to VIOS for transmission.

Unlike other reset types, a NON FATAL reset will not flush the sub crq

tx buffers. Therefore, it is possible for the batched skb array to be

partially full. So if there is call to netdev_tx_reset_queue() when

re-opening the device, the value of num_queued (0) would not account

for the skb's that are currently batched. Eventually, when the batch

is sent to VIOS, the call to netdev_tx_completed_queue() would increase

num_completed to a value greater than the num_queued. This causes a

BUG_ON crash:

ibmvnic 30000002: Firmware reports error, cause: adapter problem.

Starting recovery...

ibmvnic 30000002: tx error 600

ibmvnic 30000002: tx error 600

ibmvnic 30000002: tx error 600

ibmvnic 30000002: tx error 600

------------[ cut here ]------------

kernel BUG at lib/dynamic_queue_limits.c:27!

Oops: Exception in kernel mode, sig: 5

[....]

NIP dql_completed+0x28/0x1c0

LR ibmvnic_complete_tx.isra.0+0x23c/0x420 [ibmvnic]

Call Trace:

ibmvnic_complete_tx.isra.0+0x3f8/0x420 [ibmvnic] (unreliable)

ibmvnic_interrupt_tx+0x40/0x70 [ibmvnic]

__handle_irq_event_percpu+0x98/0x270

---[ end trace ]---

Therefore, do not reset the dql stats when performing a NON_FATAL reset.