4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ilya Dryomov <idryomov@xxxxxxxxx> commit 9c55ad1c214d9f8c4594ac2c3fa392c1c32431a7 upstream. ceph_con_workfn() validates con->state before calling try_read() and then try_write(). However, try_read() temporarily releases con->mutex, notably in process_message() and ceph_con_in_msg_alloc(), opening the window for ceph_con_close() to sneak in, close the connection and release con->sock. When try_write() is called on the assumption that con->state is still valid (i.e. not STANDBY or CLOSED), a NULL sock gets passed to the networking stack: BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 IP: selinux_socket_sendmsg+0x5/0x20 Make sure con->state is valid at the top of try_write() and add an explicit BUG_ON for this, similar to try_read(). Cc: stable@xxxxxxxxxxxxxxx Link: https://tracker.ceph.com/issues/23706 Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx> Reviewed-by: Jason Dillaman <dillaman@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ceph/messenger.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c @@ -2531,6 +2531,11 @@ static int try_write(struct ceph_connect int ret = 1; dout("try_write start %p state %lu\n", con, con->state); + if (con->state != CON_STATE_PREOPEN && + con->state != CON_STATE_CONNECTING && + con->state != CON_STATE_NEGOTIATING && + con->state != CON_STATE_OPEN) + return 0; more: dout("try_write out_kvec_bytes %d\n", con->out_kvec_bytes); @@ -2556,6 +2561,8 @@ more: } more_kvec: + BUG_ON(!con->sock); + /* kvec data queued? */ if (con->out_kvec_left) { ret = write_partial_kvec(con);
