Re: [PATCH net] mctp i3c: Fix locking in an error path

[Paolo Abeni]

On 10/26/26 20:59, Bart Van Assche wrote:
> If netdev_alloc_skb() fails, mctp_i3c_read() jumps to a label that
> unlocks mi->lock although that mutex has not been locked yet. Fix this
> by jumping to a label that only frees the skb. This bug has been
> detected by the Clang thread-safety analyzer.
>
> Cc: Leo Yang <Leo-Yang@xxxxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: Jeremy Kerr <jk@xxxxxxxxxxxxxxxxxxxx>
> Cc: Matt Johnston <matt@xxxxxxxxxxxxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Fixes: 2d2d4f60ed26 ("mctp i3c: fix MCTP I3C driver multi-thread issue")
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
>   drivers/net/mctp/mctp-i3c.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/mctp/mctp-i3c.c b/drivers/net/mctp/mctp-i3c.c
> index 4e857dd5df64..59e7bf56fce3 100644
> --- a/drivers/net/mctp/mctp-i3c.c
> +++ b/drivers/net/mctp/mctp-i3c.c
> @@ -112,7 +112,7 @@ static int mctp_i3c_read(struct mctp_i3c_device *mi)
>   	if (!skb) {
>   		stats->rx_dropped++;
>   		rc = -ENOMEM;
> -		goto err;
> +		goto free_skb;

Why the additional churn? Just return -ENOMEM, no point in freeing a NULL skb.

/P