From: Vincent Choiniere <[email protected]>
ice_tx_hang_reporter_dump() always reads tx_ring->tx_buf[0].skb,
regardless of next_to_clean. The Tx cleanup path frees the skb and
marks the buffer empty without clearing the skb pointer, so slot 0 can
hold a stale pointer. A NULL check alone does not cover this, and
devlink_fmsg_dump_skb() can fault on the freed skb.
Read tx_buf[next_to_clean] instead, use its skb only if the buffer type
is ICE_TX_BUF_SKB, and skip the skb dump otherwise.
Observed on an E810 PF passed through to a KVM guest (Ubuntu 7.0.0-14,
PREEMPT_RT, local scheduler patch): a delayed queue IRQ led to a Tx
timeout and a page fault in devlink_fmsg_dump_skb():
BUG: unable to handle page fault for address: 0000000004cd0c11
Workqueue: ice ice_service_task [ice]
RIP: devlink_fmsg_dump_skb+0x2d8/0x5d0
Call Trace:
ice_tx_hang_reporter_dump+0x1ce/0x210 [ice]
devlink_health_do_dump+0xcc/0x190
devlink_health_report+0x1d7/0x260
ice_report_tx_hang+0x7d/0xa0 [ice]
With this change and auto_dump enabled, starving a queue IRQ thread
reproduced the Tx timeout; the dump contained the test packet, no Oops
occurred and the PF recovered.
Fixes: 2a82874a3b7b ("ice: add Tx hang devlink health reporter")
Link:
https://lore.kernel.org/all/[email protected]/
Cc: [email protected]
Signed-off-by: Vincent Choiniere <[email protected]>
---
This complements the NULL check in [1]. With only that check, a non-NULL
but stale tx_buf[0].skb is still dereferenced by devlink_fmsg_dump_skb().
I have only reproduced the crash on an Ubuntu 7.0.0-14 kernel with
PREEMPT_RT and a local scheduler patch, and the skb lifetime against
concurrent Tx cleanup still needs review. Feedback welcome.
In my case next_to_clean was 0xfc while the reporter read slot 0.
Upstream v7.0, v7.2 and current net main (191aa4154) all read
tx_buf[0].skb unconditionally. Before this change, recovery stayed
stuck until reboot.
[1]
https://lore.kernel.org/all/[email protected]/
---
drivers/net/ethernet/intel/ice/devlink/health.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/intel/ice/devlink/health.c
b/drivers/net/ethernet/intel/ice/devlink/health.c
index 8e9a8a817..059859c36 100644
--- a/drivers/net/ethernet/intel/ice/devlink/health.c
+++ b/drivers/net/ethernet/intel/ice/devlink/health.c
@@ -390,12 +390,15 @@ static int ice_tx_hang_reporter_dump(struct
devlink_health_reporter *reporter,
struct netlink_ext_ack *extack)
{
struct ice_tx_hang_event *event = priv_ctx;
- struct sk_buff *skb;
+ struct sk_buff *skb = NULL;
+ struct ice_tx_buf *tx_buf;
if (!event)
return 0;
- skb = event->tx_ring->tx_buf->skb;
+ tx_buf = &event->tx_ring->tx_buf[event->next_to_clean];
+ if (tx_buf->type == ICE_TX_BUF_SKB)
+ skb = tx_buf->skb;
devlink_fmsg_obj_nest_start(fmsg);
ICE_DEVLINK_FMSG_PUT_FIELD(fmsg, event, head);
ICE_DEVLINK_FMSG_PUT_FIELD(fmsg, event, intr);
@@ -409,7 +412,8 @@ static int ice_tx_hang_reporter_dump(struct
devlink_health_reporter *reporter,
ice_fmsg_put_ptr(fmsg, "skb-ptr", skb);
devlink_fmsg_binary_pair_put(fmsg, "desc", event->tx_ring->desc,
event->tx_ring->count * sizeof(struct
ice_tx_desc));
- devlink_fmsg_dump_skb(fmsg, skb);
+ if (skb)
+ devlink_fmsg_dump_skb(fmsg, skb);
devlink_fmsg_obj_nest_end(fmsg);
return 0;
---
base-commit: 191aa41548b2d2b6af534a6d5cf84a552435c74c
change-id: 20261016-ice-tx-hang-dump-e46b4ed483d6
Best regards,
--
Vincent Choiniere <[email protected]>
