On Thu, May 28, 2026 at 11:30:39AM +0200, Paolo Abeni wrote:

On 5/25/26 10:08 AM, Dipayaan Roy wrote:

quoted

When mana_per_port_queue_reset_work_handler() runs after a previous
detach succeeded but attach failed, the port is left in a detached
state with apc->tx_qp and apc->rxqs already freed. Calling
mana_detach() again unconditionally leads to NULL pointer dereferences
during queue teardown.

Add an early exit in mana_detach() when the port is already in
detached state (!netif_device_present) for non-close callers, making
it safe to call idempotently. This allows the queue reset handler and
other recovery paths to simply retry mana_attach() without redundant
teardown.

Fixes: 3b194343c250 ("net: mana: Implement ndo_tx_timeout and serialize queue resets per port.")
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Dipayaan Roy <redacted>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 0582803907a8..1e1ad2795c3c 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c

@@ -3350,6 +3350,12 @@ int mana_detach(struct net_device *ndev, bool from_close)
 
 	ASSERT_RTNL();
 
+	/* If already detached (indicates detach succeeded but attach failed
+	 * previously). Now skip mana detach and just retry mana_attach.
+	 */
+	if (!from_close && !netif_device_present(ndev))
+		return 0;
+
 	apc->port_st_save = apc->port_is_up;
 	apc->port_is_up = false;

sashiko(gemini) notes the above can lead to different race:

---
Can this early return cause state machine corruption by bypassing the
updates
to apc->port_st_save?
Consider this sequence:
1. queue_reset_work runs, mana_detach() succeeds (apc->port_st_save = true,
   apc->port_is_up = false), but mana_attach() fails.
2. The admin brings the interface down (ip link set dev eth0 down), skipping
   mana_close() since apc->port_is_up is false.
3. The admin changes the MTU, triggering mana_change_mtu() which calls
   mana_detach() followed by mana_attach().
4. mana_detach() hits this new early return, preserving
   apc->port_st_save == true.
When mana_attach() runs, it sees apc->port_st_save == true and allocates
queues, setting apc->vport_use_count = 1 and apc->port_is_up = true, even
though the interface is administratively down.
If the admin then brings the interface up, mana_open() will unconditionally
call mana_alloc_queues(). That function calls mana_cfg_vport(), which will
return -EBUSY because apc->vport_use_count is already 1.
This leaves mana_open() failing and the interface down. Since the interface
is already down, trying to bring it down again is a no-op, meaning
mana_close() is never called to clean up the orphaned queues.
Does this sequence permanently brick the port until the driver is reloaded?
---

I think you need to be more restrictive in the early return check.

/P

Hi Paolo,

Thank you for the comments,
I think the scenario pointed out by sashiko does not seems valid,
as it mentioned in step 2 and 3 admin changing MTU after bringing
interface down. This is becasue netif_set_mtu_ext() in dev.c checks
netif_device_present and returns -ENODEV before calling
ndo_change_mtu. So mana_change_mtu() is never reachable when the
device is in the !present state.

https://elixir.bootlin.com/linux/v7.0/source/net/core/dev.c#L9906 

Please let me know if the above check is good enough?

Regards
Dipayaan Roy