RE: [PATCH] net: lan743x: Initialize eth_syslock spinlock before use

[David Thompson]

> -----Original Message-----
> From: Andrea Righi <arighi@xxxxxxxxxx>
> Sent: Friday, June 26, 2026 12:32 PM
> To: Bryan Whitehead <bryan.whitehead@xxxxxxxxxxxxx>;
> UNGLinuxDriver@xxxxxxxxxxxxx
> Cc: Andrew Lunn <andrew+netdev@xxxxxxx>; David S . Miller
> <davem@xxxxxxxxxxxxx>; Eric Dumazet <edumazet@xxxxxxxxxx>; Jakub
> Kicinski <kuba@xxxxxxxxxx>; Paolo Abeni <pabeni@xxxxxxxxxx>; Raju
> Lakkaraju <Raju.Lakkaraju@xxxxxxxxxxxxx>; David Thompson
> <davthompson@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: [PATCH] net: lan743x: Initialize eth_syslock spinlock before use
> 
> lan743x_hardware_init() calls pci11x1x_strap_get_status() during the PCI11x1x
> probe sequence. That helper acquires the Ethernet subsystem hardware lock
> via lan743x_hs_syslock_acquire(), which relies on
> adapter->eth_syslock_spinlock to serialize access.
> 
> The spinlock is currently initialized only after the strap status is read. With
> CONFIG_DEBUG_SPINLOCK enabled, taking the zeroed initialized spinlock can
> trip the spinlock debug check.
> 
> Fix by initializing adapter->eth_syslock_spinlock before reading the strap status
> so the probe path never attempts to lock an uninitialized spinlock.
> 
> Fixes: 46b777ad9a8c ("net: lan743x: Add support to SGMII 1G and 2.5G")
> Cc: stable@xxxxxxxxxxxxxxx # v6.0+
> Signed-off-by: Andrea Righi <arighi@xxxxxxxxxx>
> ---
>  drivers/net/ethernet/microchip/lan743x_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/microchip/lan743x_main.c
> b/drivers/net/ethernet/microchip/lan743x_main.c
> index 1cdce35e14239..e759171bfd766 100644
> --- a/drivers/net/ethernet/microchip/lan743x_main.c
> +++ b/drivers/net/ethernet/microchip/lan743x_main.c
> @@ -3541,8 +3541,8 @@ static int lan743x_hardware_init(struct
> lan743x_adapter *adapter,
>  		adapter->max_tx_channels = PCI11X1X_MAX_TX_CHANNELS;
>  		adapter->used_tx_channels = PCI11X1X_USED_TX_CHANNELS;
>  		adapter->max_vector_count =
> PCI11X1X_MAX_VECTOR_COUNT;
> -		pci11x1x_strap_get_status(adapter);
>  		spin_lock_init(&adapter->eth_syslock_spinlock);
> +		pci11x1x_strap_get_status(adapter);
>  		mutex_init(&adapter->sgmii_rw_lock);
>  		pci11x1x_set_rfe_rd_fifo_threshold(adapter);
>  		sgmii_ctl = lan743x_csr_read(adapter, SGMII_CTL);
> --
> 2.54.0

Reviewed-by: David Thompson <davthompson@xxxxxxxxxx>