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net: thunderx: avoid direct MTU assignment after WRITE_ONCE()

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The current logic in nicvf_change_mtu() writes the new MTU to
netdev->mtu using WRITE_ONCE() before verifying if the hardware
update succeeds. However on hardware update failure, it attempts
to revert to the original MTU using a direct assignment
(netdev->mtu = orig_mtu)
which violates the intended of WRITE_ONCE protection introduced in
commit 1eb2cded45 ("net: annotate writes on dev->mtu from
ndo_change_mtu()")

Additionally, WRITE_ONCE(netdev->mtu, new_mtu) is unnecessarily
performed even when the device is not running.

Fix this by:
  Only writing netdev->mtu after successfully updating the hardware.
  Skipping hardware update when the device is down, and setting MTU
  directly. Remove unused variable orig_mtu.

This ensures that all writes to netdev->mtu are consistent with
WRITE_ONCE expectations and avoids unintended state corruption
on failure paths.

Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250706194327.1369390-1-alok.a.tiwari@oracle.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Alok Tiwari 2025-07-06 12:43:21 -07:00 committed by Jakub Kicinski
parent d55683866c
commit 849704b8b2
1 changed files with 3 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/net/ethernet/cavium/thunder/nicvf_main.c
View File

@ -1578,7 +1578,6 @@ int nicvf_open(struct net_device *netdev)
static int nicvf_change_mtu(struct net_device *netdev, int new_mtu)
{
struct nicvf *nic = netdev_priv(netdev);
int orig_mtu = netdev->mtu;
/* For now just support only the usual MTU sized frames,
* plus some headroom for VLAN, QinQ.
@ -1589,15 +1588,10 @@ static int nicvf_change_mtu(struct net_device *netdev, int new_mtu)
return -EINVAL;
}
WRITE_ONCE(netdev->mtu, new_mtu);
if (!netif_running(netdev))
return 0;
if (nicvf_update_hw_max_frs(nic, new_mtu)) {
netdev->mtu = orig_mtu;
if (netif_running(netdev) && nicvf_update_hw_max_frs(nic, new_mtu))
return -EINVAL;
}
WRITE_ONCE(netdev->mtu, new_mtu);
return 0;
}