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SubjectRe: [PATCH] libceph: protect pending flags in ceph_con_keepalive()
On Thu, Dec 27, 2018 at 8:08 PM Myungho Jung <mhjungk@gmail.com> wrote:
>
> con_flag_test_and_set() sets CON_FLAG_KEEPALIVE_PENDING and
> CON_FLAG_WRITE_PENDING flags without protection in ceph_con_keepalive().
> It triggers WARN_ON() in clear_standby() if the flags are set after
> con_fault() changes connection state to CON_STATE_STANDBY. Move
> con_flag_test_and_set() to be called before releasing the lock and store
> the condition to check after the critical section.
>
> Reported-by: syzbot+acdeb633f6211ccdf886@syzkaller.appspotmail.com
> Signed-off-by: Myungho Jung <mhjungk@gmail.com>
> ---
> net/ceph/messenger.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 2f126eff275d..e15da22d4f37 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -3216,12 +3216,16 @@ void ceph_msg_revoke_incoming(struct ceph_msg *msg)
> */
> void ceph_con_keepalive(struct ceph_connection *con)
> {
> + bool pending;
> +
> dout("con_keepalive %p\n", con);
> mutex_lock(&con->mutex);
> clear_standby(con);
> + pending = (con_flag_test_and_set(con,
> + CON_FLAG_KEEPALIVE_PENDING) == 0 &&
> + con_flag_test_and_set(con, CON_FLAG_WRITE_PENDING) == 0);
> mutex_unlock(&con->mutex);
> - if (con_flag_test_and_set(con, CON_FLAG_KEEPALIVE_PENDING) == 0 &&
> - con_flag_test_and_set(con, CON_FLAG_WRITE_PENDING) == 0)
> + if (pending)
> queue_con(con);
> }
> EXPORT_SYMBOL(ceph_con_keepalive);

Hi Myungho,

Were you able to reproduce? If so, did you use the syzkaller output or
something else?

Thanks,

Ilya

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