[PATCH v2] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

[Dmitry Eremin]

From: Dmitry Eremin <Dmitry.Eremin@xxxxxxxxx>

The logic of the original commit 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
was assumed conditional free of struct kib_conn if the second argument free_conn
in function kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn) is true.
But this hunk of code was dropped from original commit. As result the logic
works wrong and current code use struct kib_conn after free.

> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
> 3317  kiblnd_destroy_conn(conn, !peer);
>                           ^^^^ Freed always (but should be conditionally)
> 3318
> 3319  spin_lock_irqsave(lock, flags);
> 3320  if (!peer)
> 3321      continue;
> 3322
> 3323  conn->ibc_peer = peer;
>       ^^^^^^^^^^^^^^ Use after free
> 3324  if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
> 3325      list_add_tail(&conn->ibc_list,
>                          ^^^^^^^^^^^^^^ Use after free
> 3326                    &kiblnd_data.kib_reconn_list);
> 3327  else
> 3328      list_add_tail(&conn->ibc_list,
>                          ^^^^^^^^^^^^^^ Use after free
> 3329                    &kiblnd_data.kib_reconn_wait);

After attached patch this code will use struct kib_conn only when it was not freed.

Cc: <stable@xxxxxxxxxxxxxxx> # v4.6
Fixes: 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
Signed-off-by: Dmitry Eremin <Dmitry.Eremin@xxxxxxxxx>
Signed-off-by: Dmitry Eremin <dmitry.eremin@xxxxxxxxx>
---
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
index 2ebc484385b3..a15a625ee9b6 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
@@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
 		atomic_dec(&net->ibn_nconns);
 	}
 
-	kfree(conn);
+	if (free_conn)
+		kfree(conn);
 }
 
 int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)
-- 
1.8.3.1


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