[PATCH v4] staging: lustre: separate a connection destroy from free struct kib_conn

From: Dmitry Eremin
Date: Thu Jan 25 2018 - 08:51:41 EST


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);

To avoid confusion this fix moved the freeing a struct kib_conn outside of
the function kiblnd_destroy_conn() and free as it was intended in original
commit.

Cc: <stable@xxxxxxxxxxxxxxx> # v4.6
Fixes: 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
Signed-off-by: Dmitry Eremin <Dmitry.Eremin@xxxxxxxxx>
---
Changes in v4:
- fixed the issue with use after free by moving the freeing a struct
kib_conn outside of the function kiblnd_destroy_conn()

drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 7 +++----
drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h | 2 +-
drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c | 6 ++++--
3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
index 2ebc484385b3..ec84edfda271 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
@@ -824,14 +824,15 @@ struct kib_conn *kiblnd_create_conn(struct kib_peer *peer, struct rdma_cm_id *cm
return conn;

failed_2:
- kiblnd_destroy_conn(conn, true);
+ kiblnd_destroy_conn(conn);
+ kfree(conn);
failed_1:
kfree(init_qp_attr);
failed_0:
return NULL;
}

-void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
+void kiblnd_destroy_conn(struct kib_conn *conn)
{
struct rdma_cm_id *cmid = conn->ibc_cmid;
struct kib_peer *peer = conn->ibc_peer;
@@ -889,8 +890,6 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
rdma_destroy_id(cmid);
atomic_dec(&net->ibn_nconns);
}
-
- kfree(conn);
}

int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)
diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
index 171eced213f8..b18911d09e9a 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
@@ -1016,7 +1016,7 @@ int kiblnd_close_stale_conns_locked(struct kib_peer *peer,
struct kib_conn *kiblnd_create_conn(struct kib_peer *peer,
struct rdma_cm_id *cmid,
int state, int version);
-void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn);
+void kiblnd_destroy_conn(struct kib_conn *conn);
void kiblnd_close_conn(struct kib_conn *conn, int error);
void kiblnd_close_conn_locked(struct kib_conn *conn, int error);

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
index 9b3328c5d1e7..b3e7f28eb978 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
@@ -3314,11 +3314,13 @@ static int kiblnd_resolve_addr(struct rdma_cm_id *cmid,
spin_unlock_irqrestore(lock, flags);
dropped_lock = 1;

- kiblnd_destroy_conn(conn, !peer);
+ kiblnd_destroy_conn(conn);

spin_lock_irqsave(lock, flags);
- if (!peer)
+ if (!peer) {
+ kfree(conn);
continue;
+ }

conn->ibc_peer = peer;
if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
--
1.8.3.1


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