Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 10 May 2017 18:51:31 +0300 | From | Ido Schimmel <> | Subject | Re: [net-mellanox] question about potential null pointer dereference |
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On Wed, May 10, 2017 at 10:36:59AM -0500, Gustavo A. R. Silva wrote: > > Hello everybody, > > While looking into Coverity ID 1350941 I ran into the following piece of > code at drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c:1483: > > 1483static void mlxsw_sp_fdb_notify_mac_process(struct mlxsw_sp *mlxsw_sp, > 1484 char *sfn_pl, int rec_index, > 1485 bool adding) > 1486{ > 1487 struct mlxsw_sp_port *mlxsw_sp_port; > 1488 char mac[ETH_ALEN]; > 1489 u8 local_port; > 1490 u16 vid, fid; > 1491 bool do_notification = true; > 1492 int err; > 1493 > 1494 mlxsw_reg_sfn_mac_unpack(sfn_pl, rec_index, mac, &fid, > &local_port); > 1495 mlxsw_sp_port = mlxsw_sp->ports[local_port]; > 1496 if (!mlxsw_sp_port) { > 1497 dev_err_ratelimited(mlxsw_sp->bus_info->dev, "Incorrect > local port in FDB notification\n"); > 1498 goto just_remove; > 1499 } > 1500 > 1501 if (mlxsw_sp_fid_is_vfid(fid)) { > 1502 struct mlxsw_sp_port *mlxsw_sp_vport; > 1503 > 1504 mlxsw_sp_vport = > mlxsw_sp_port_vport_find_by_fid(mlxsw_sp_port, > 1505 fid); > 1506 if (!mlxsw_sp_vport) { > 1507 netdev_err(mlxsw_sp_port->dev, "Failed to find a > matching vPort following FDB notification\n"); > 1508 goto just_remove; > 1509 } > 1510 vid = 0; > 1511 /* Override the physical port with the vPort. */ > 1512 mlxsw_sp_port = mlxsw_sp_vport; > 1513 } else { > 1514 vid = fid; > 1515 } > 1516 > 1517do_fdb_op: > 1518 err = mlxsw_sp_port_fdb_uc_op(mlxsw_sp, local_port, mac, fid, > 1519 adding, true); > 1520 if (err) { > 1521 if (net_ratelimit()) > 1522 netdev_err(mlxsw_sp_port->dev, "Failed to set > FDB entry\n"); > 1523 return; > 1524 } > 1525 > 1526 if (!do_notification) > 1527 return; > 1528 mlxsw_sp_fdb_call_notifiers(mlxsw_sp_port->learning_sync, > 1529 adding, mac, vid, mlxsw_sp_port->dev); > 1530 return; > 1531 > 1532just_remove: > 1533 adding = false; > 1534 do_notification = false; > 1535 goto do_fdb_op; > 1536} > > > The issue here is that line 1496 implies that mlxsw_sp_port might be NULL. > If this is the case, the execution path jumps to line 1532 and then to line > 1517. All this could end up dereferencing a NULL pointer at line 1522. > > Is there any chance for mlxsw_sp_port to be NULL at line 1496 and, at the > same time, a NULL pointer dereference occurs at line 1522? > > I'm trying to figure out if this is a false positive or something that > actually needs to be fixed.
In theory, yes, it can happen, but it didn't happen yet. I recently patched that and now it's in Jiri's queue. I guess he'll send it tomorrow.
https://github.com/jpirko/linux_mlxsw/commit/4160fb9ad6eeacba7736cfdbf7f52248432c2e89
Thanks for looking into this!
> > I'd really appreciate any comment on this. > Thank you! > -- > Gustavo A. R. Silva
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