From 6dc43cd3aae0ffeeaebe427e1bf5e5faf9de7d42 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Sat, 25 Jan 2020 23:01:11 +0200 Subject: net: dsa: Fix use-after-free in probing of DSA switch tree DSA sets up a switch tree little by little. Every switch of the N members of the tree calls dsa_register_switch, and (N - 1) will just touch the dst->ports list with their ports and quickly exit. Only the last switch that calls dsa_register_switch will find all DSA links complete in dsa_tree_setup_routing_table, and not return zero as a result but instead go ahead and set up the entire DSA switch tree (practically on behalf of the other switches too). The trouble is that the (N - 1) switches don't clean up after themselves after they get an error such as EPROBE_DEFER. Their footprint left in dst->ports by dsa_switch_touch_ports is still there. And switch N, the one responsible with actually setting up the tree, is going to work with those stale dp, dp->ds and dp->ds->dev pointers. In particular ds and ds->dev might get freed by the device driver. Be there a 2-switch tree and the following calling order: - Switch 1 calls dsa_register_switch - Calls dsa_switch_touch_ports, populates dst->ports - Calls dsa_port_parse_cpu, gets -EPROBE_DEFER, exits. - Switch 2 calls dsa_register_switch - Calls dsa_switch_touch_ports, populates dst->ports - Probe doesn't get deferred, so it goes ahead. - Calls dsa_tree_setup_routing_table, which returns "complete == true" due to Switch 1 having called dsa_switch_touch_ports before. - Because the DSA links are complete, it calls dsa_tree_setup_switches now. - dsa_tree_setup_switches iterates through dst->ports, initializing the Switch 1 ds structure (invalid) and the Switch 2 ds structure (valid). - Undefined behavior (use after free, sometimes NULL pointers, etc). Real example below (debugging prints added by me, as well as guards against NULL pointers): [ 5.477947] dsa_tree_setup_switches: Setting up port 0 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.313002] dsa_tree_setup_switches: Setting up port 1 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.319932] dsa_tree_setup_switches: Setting up port 2 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.329693] dsa_tree_setup_switches: Setting up port 3 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.339458] dsa_tree_setup_switches: Setting up port 4 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.349226] dsa_tree_setup_switches: Setting up port 5 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.358991] dsa_tree_setup_switches: Setting up port 6 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.368758] dsa_tree_setup_switches: Setting up port 7 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.378524] dsa_tree_setup_switches: Setting up port 8 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.388291] dsa_tree_setup_switches: Setting up port 9 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.398057] dsa_tree_setup_switches: Setting up port 10 of switch ffffff803df0b980 (dev ffffff803f775c00) [ 6.407912] dsa_tree_setup_switches: Setting up port 0 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.417682] dsa_tree_setup_switches: Setting up port 1 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.427446] dsa_tree_setup_switches: Setting up port 2 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.437212] dsa_tree_setup_switches: Setting up port 3 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.446979] dsa_tree_setup_switches: Setting up port 4 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.456744] dsa_tree_setup_switches: Setting up port 5 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.466512] dsa_tree_setup_switches: Setting up port 6 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.476277] dsa_tree_setup_switches: Setting up port 7 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.486043] dsa_tree_setup_switches: Setting up port 8 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.495810] dsa_tree_setup_switches: Setting up port 9 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.505577] dsa_tree_setup_switches: Setting up port 10 of switch ffffff803da02f80 (dev 0000000000000000) [ 6.515433] dsa_tree_setup_switches: Setting up port 0 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.354120] dsa_tree_setup_switches: Setting up port 1 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.361045] dsa_tree_setup_switches: Setting up port 2 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.370805] dsa_tree_setup_switches: Setting up port 3 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.380571] dsa_tree_setup_switches: Setting up port 4 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.390337] dsa_tree_setup_switches: Setting up port 5 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.400104] dsa_tree_setup_switches: Setting up port 6 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.409872] dsa_tree_setup_switches: Setting up port 7 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.419637] dsa_tree_setup_switches: Setting up port 8 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.429403] dsa_tree_setup_switches: Setting up port 9 of switch ffffff803db15b80 (dev ffffff803d8e4800) [ 7.439169] dsa_tree_setup_switches: Setting up port 10 of switch ffffff803db15b80 (dev ffffff803d8e4800) The solution is to recognize that the functions that call dsa_switch_touch_ports (dsa_switch_parse_of, dsa_switch_parse) have side effects, and therefore one should clean up their side effects on error path. The cleanup of dst->ports was taken from dsa_switch_remove and moved into a dedicated dsa_switch_release_ports function, which should really be per-switch (free only the members of dst->ports that are also members of ds, instead of all switch ports). Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller --- net/dsa/dsa2.c | 36 +++++++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 11 deletions(-) (limited to 'net') diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c index c6d81f2baf4e..e7c30b472034 100644 --- a/net/dsa/dsa2.c +++ b/net/dsa/dsa2.c @@ -849,6 +849,19 @@ static int dsa_switch_parse(struct dsa_switch *ds, struct dsa_chip_data *cd) return dsa_switch_parse_ports(ds, cd); } +static void dsa_switch_release_ports(struct dsa_switch *ds) +{ + struct dsa_switch_tree *dst = ds->dst; + struct dsa_port *dp, *next; + + list_for_each_entry_safe(dp, next, &dst->ports, list) { + if (dp->ds != ds) + continue; + list_del(&dp->list); + kfree(dp); + } +} + static int dsa_switch_probe(struct dsa_switch *ds) { struct dsa_switch_tree *dst; @@ -865,12 +878,17 @@ static int dsa_switch_probe(struct dsa_switch *ds) if (!ds->num_ports) return -EINVAL; - if (np) + if (np) { err = dsa_switch_parse_of(ds, np); - else if (pdata) + if (err) + dsa_switch_release_ports(ds); + } else if (pdata) { err = dsa_switch_parse(ds, pdata); - else + if (err) + dsa_switch_release_ports(ds); + } else { err = -ENODEV; + } if (err) return err; @@ -878,8 +896,10 @@ static int dsa_switch_probe(struct dsa_switch *ds) dst = ds->dst; dsa_tree_get(dst); err = dsa_tree_setup(dst); - if (err) + if (err) { + dsa_switch_release_ports(ds); dsa_tree_put(dst); + } return err; } @@ -900,15 +920,9 @@ EXPORT_SYMBOL_GPL(dsa_register_switch); static void dsa_switch_remove(struct dsa_switch *ds) { struct dsa_switch_tree *dst = ds->dst; - struct dsa_port *dp, *next; dsa_tree_teardown(dst); - - list_for_each_entry_safe(dp, next, &dst->ports, list) { - list_del(&dp->list); - kfree(dp); - } - + dsa_switch_release_ports(ds); dsa_tree_put(dst); } -- cgit v1.2.3