linux-kernel - Re: [PATCH] tg3: Check return value of tg3_nvram

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Message-ID: <CACKFLikfW2yLUmZpJPE=npeUi-LBaDyNFVVPt_FA+4bYdhvEEQ@mail.gmail.com>
Date: Tue, 11 Feb 2025 13:50:00 -0800
From: Michael Chan <michael.chan@...adcom.com>
To: Wentao Liang <vulab@...as.ac.cn>
Cc: pavan.chebbi@...adcom.com, mchan@...adcom.com, andrew+netdev@...n.ch, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tg3: Check return value of tg3_nvram_lock before
 resetting lock

On Tue, Feb 11, 2025 at 7:27 AM Wentao Liang <vulab@...as.ac.cn> wrote:
>
> The current code does not check the return value of tg3_nvram_lock before
> resetting the lock count (tp->nvram_lock_cnt = 0). This is dangerous
> because if tg3_nvram_lock fails, the lock state may be inconsistent,
> leading to potential race conditions or undefined behavior.
>
> This patch adds a check for the return value of tg3_nvram_lock. If the
> function fails, the error is propagated to the caller, ensuring that
> the lock state remains consistent.
>
> Signed-off-by: Wentao Liang <vulab@...as.ac.cn>
> ---
>  drivers/net/ethernet/broadcom/tg3.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
> index 9cc8db10a8d6..851d19b3f43c 100644
> --- a/drivers/net/ethernet/broadcom/tg3.c
> +++ b/drivers/net/ethernet/broadcom/tg3.c
> @@ -9160,7 +9160,9 @@ static int tg3_chip_reset(struct tg3 *tp)
>         if (!pci_device_is_present(tp->pdev))
>                 return -ENODEV;
>
> -       tg3_nvram_lock(tp);
> +       err = tg3_nvram_lock(tp);
> +       if (err)
> +               return err;

It is correct not to check the return value here since we are about to
reset the chip.  The nvram lock is a hardware arbitration lock that is
granted by the hardware.  If the hardware is in a bad state, we may
not get the lock but we should still proceed to reset.  A few lines
below this we reset the tp->nvram_lock_cnt to 0 so it is safe.

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