Re: [PATCH] net/smc: fix sock refcount leak in smc_switch_conns() error path

Hi Yifei,

Thanks for looking into this.

Yes I have submitted a patch for the same issue.
https://lore.kernel.org/netdev/[email protected]/

Hidayath

On 05/08/26 3:09 am, Yifei Gao wrote:
> smc_switch_conns() takes a reference on the socket with sock_hold() before
> dropping conns_lock to prefetch a tx slot. On success the reference is
> released by the sock_put() after smc_switch_cursor(). When
> smc_cdc_get_free_slot() fails, however, the function jumps straight to
> err_out without a sock_put(), leaking the reference and leaving the socket
> unreclaimable. During SMC-R link failover with an exhausted backup link
> this leaks one reference per failing connection switch.
>
> Release the reference before jumping to err_out. The err_out label is also
> reached from the smc_switch_cursor() failure path, which has already done
> its own sock_put(), so the put must stay at the get_free_slot failure site
> rather than at the label.
>
> Fixes: c6f02ebeea3a ("net/smc: switch connections to alternate link")
> Cc: [email protected]
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Yifei Gao <[email protected]>
> ---
>   net/smc/smc_core.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
> index cf6b620fef05..04c6ce608ec7 100644
> --- a/net/smc/smc_core.c
> +++ b/net/smc/smc_core.c
> @@ -1148,8 +1148,10 @@ struct smc_link *smc_switch_conns(struct smc_link_group *lgr,
>   		read_unlock_bh(&lgr->conns_lock);
>   		/* pre-fetch buffer outside of send_lock, might sleep */
>   		rc = smc_cdc_get_free_slot(conn, to_lnk, &wr_buf, NULL, &pend);
> -		if (rc)
> +		if (rc) {
> +			sock_put(&smc->sk);
>   			goto err_out;
> +		}
>   		/* avoid race with smcr_tx_sndbuf_nonempty() */
>   		spin_lock_bh(&conn->send_lock);
>   		smc_switch_link_and_count(conn, to_lnk);