[rds-devel] [External] : Re: [PATCH net] rds: ib: use rds_conn_drop() on protocol version mismatch

[Allison Henderson]

On Tue, 2026-09-08 at 20:33 +0800, henrymei wrote:
> From: Aohan Mei <henrymei at tencent.com>
> 
> rds_ib_cm_connect_complete() runs from the RDMA-CM event handler with
> conn->c_cm_lock held.  When the peer negotiates a protocol version
> older than RDS_PROTOCOL_COMPAT_VERSION, the handler calls
> rds_conn_destroy(), which is only safe in the rmmod path: it
> synchronously tears the connection down and flush_work()es the
> shutdown work cp_down_w.
> 
> That shutdown work (rds_conn_shutdown()) needs cp_cm_lock, which is
> the very lock the event handler still holds, so the flush never
> completes: the two workers wait on each other and the RDS connection
> workqueues stall for good.
> 
> All other RDMA-CM failure paths (REJECTED, CONNECT_ERROR,
> DISCONNECTED) use rds_conn_drop(), which marks the connection
> RDS_CONN_ERROR and schedules the shutdown work asynchronously.  Use
> it here as well.
> 
> Fixes: cdc306a5c9cd ("rds: make v3.1 as compat version")

Hi Aohan,

Thanks for the catch, this looks correct to me.  Just one nit on the
fixes tag.  I think we want: f147dd9ecabf ("RDS/IB: Disallow connections
less than RDS 3.1").  That looks like the commit that added the
rds_conn_destroy() call to the version check.  Other than that, I think
this patch looks good.  With the Fixes tag corrected, you can add my rvb:

Reviewed-by: Allison Henderson <achender at kernel.org>

Thanks!
Allison

> Reported-by: TencentOS Corvus AI <corvus at tencent.com>
> Cc: stable at vger.kernel.org
> Assisted-by: CodeBuddy:Kimi-K3
> Signed-off-by: Aohan Mei <henrymei at tencent.com>
> ---
>  net/rds/ib_cm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c
> index d46146887ba4..2909da8363f3 100644
> --- a/net/rds/ib_cm.c
> +++ b/net/rds/ib_cm.c
> @@ -115,7 +115,7 @@ void rds_ib_cm_connect_complete(struct rds_connection *conn, struct rdma_cm_even
>  				  &conn->c_laddr, &conn->c_faddr,
>  				  RDS_PROTOCOL_MAJOR(conn->c_version),
>  				  RDS_PROTOCOL_MINOR(conn->c_version));
> -			rds_conn_destroy(conn);
> +			rds_conn_drop(conn);
>  			return;
>  		}
>  	}