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

[Tony Lu]

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

Please use [PATCH net] as the subject prefix when sending v2, since
this fix targets the net tree.

On Tue, Aug 04, 2026 at 09:39:17PM +0000, 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: stable@xxxxxxxxxxxxxxx
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Yifei Gao <gyf161023@xxxxxxxxx>
> ---
>  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);
> -- 
> 2.43.0