6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ido Schimmel idosch@nvidia.com
[ Upstream commit 8b0e69763ef948fb872a7767df4be665d18f5fd4 ]
We sometimes observe use-after-free when dereferencing a neighbour [1]. The problem seems to be that the driver stores a pointer to the neighbour, but without holding a reference on it. A reference is only taken when the neighbour is used by a nexthop.
Fix by simplifying the reference counting scheme. Always take a reference when storing a neighbour pointer in a neighbour entry. Avoid taking a referencing when the neighbour is used by a nexthop as the neighbour entry associated with the nexthop already holds a reference.
Tested by running the test that uncovered the problem over 300 times. Without this patch the problem was reproduced after a handful of iterations.
[1] BUG: KASAN: slab-use-after-free in mlxsw_sp_neigh_entry_update+0x2d4/0x310 Read of size 8 at addr ffff88817f8e3420 by task ip/3929
CPU: 3 UID: 0 PID: 3929 Comm: ip Not tainted 6.18.0-rc4-virtme-g36b21a067510 #3 PREEMPT(full) Hardware name: Nvidia SN5600/VMOD0013, BIOS 5.13 05/31/2023 Call Trace: <TASK> dump_stack_lvl+0x6f/0xa0 print_address_description.constprop.0+0x6e/0x300 print_report+0xfc/0x1fb kasan_report+0xe4/0x110 mlxsw_sp_neigh_entry_update+0x2d4/0x310 mlxsw_sp_router_rif_gone_sync+0x35f/0x510 mlxsw_sp_rif_destroy+0x1ea/0x730 mlxsw_sp_inetaddr_port_vlan_event+0xa1/0x1b0 __mlxsw_sp_inetaddr_lag_event+0xcc/0x130 __mlxsw_sp_inetaddr_event+0xf5/0x3c0 mlxsw_sp_router_netdevice_event+0x1015/0x1580 notifier_call_chain+0xcc/0x150 call_netdevice_notifiers_info+0x7e/0x100 __netdev_upper_dev_unlink+0x10b/0x210 netdev_upper_dev_unlink+0x79/0xa0 vrf_del_slave+0x18/0x50 do_set_master+0x146/0x7d0 do_setlink.isra.0+0x9a0/0x2880 rtnl_newlink+0x637/0xb20 rtnetlink_rcv_msg+0x6fe/0xb90 netlink_rcv_skb+0x123/0x380 netlink_unicast+0x4a3/0x770 netlink_sendmsg+0x75b/0xc90 __sock_sendmsg+0xbe/0x160 ____sys_sendmsg+0x5b2/0x7d0 ___sys_sendmsg+0xfd/0x180 __sys_sendmsg+0x124/0x1c0 do_syscall_64+0xbb/0xfd0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 [...]
Allocated by task 109: kasan_save_stack+0x30/0x50 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x7b/0x90 __kmalloc_noprof+0x2c1/0x790 neigh_alloc+0x6af/0x8f0 ___neigh_create+0x63/0xe90 mlxsw_sp_nexthop_neigh_init+0x430/0x7e0 mlxsw_sp_nexthop_type_init+0x212/0x960 mlxsw_sp_nexthop6_group_info_init.constprop.0+0x81f/0x1280 mlxsw_sp_nexthop6_group_get+0x392/0x6a0 mlxsw_sp_fib6_entry_create+0x46a/0xfd0 mlxsw_sp_router_fib6_replace+0x1ed/0x5f0 mlxsw_sp_router_fib6_event_work+0x10a/0x2a0 process_one_work+0xd57/0x1390 worker_thread+0x4d6/0xd40 kthread+0x355/0x5b0 ret_from_fork+0x1d4/0x270 ret_from_fork_asm+0x11/0x20
Freed by task 154: kasan_save_stack+0x30/0x50 kasan_save_track+0x14/0x30 __kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x43/0x70 kmem_cache_free_bulk.part.0+0x1eb/0x5e0 kvfree_rcu_bulk+0x1f2/0x260 kfree_rcu_work+0x130/0x1b0 process_one_work+0xd57/0x1390 worker_thread+0x4d6/0xd40 kthread+0x355/0x5b0 ret_from_fork+0x1d4/0x270 ret_from_fork_asm+0x11/0x20
Last potentially related work creation: kasan_save_stack+0x30/0x50 kasan_record_aux_stack+0x8c/0xa0 kvfree_call_rcu+0x93/0x5b0 mlxsw_sp_router_neigh_event_work+0x67d/0x860 process_one_work+0xd57/0x1390 worker_thread+0x4d6/0xd40 kthread+0x355/0x5b0 ret_from_fork+0x1d4/0x270 ret_from_fork_asm+0x11/0x20
Fixes: 6cf3c971dc84 ("mlxsw: spectrum_router: Add private neigh table") Signed-off-by: Ido Schimmel idosch@nvidia.com Reviewed-by: Petr Machata petrm@nvidia.com Signed-off-by: Petr Machata petrm@nvidia.com Reviewed-by: Simon Horman horms@kernel.org Link: https://patch.msgid.link/92d75e21d95d163a41b5cea67a15cd33f547cba6.1764695650... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- .../ethernet/mellanox/mlxsw/spectrum_router.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c index a00dd0ee524e1..3fa790c5ef747 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c @@ -2163,6 +2163,7 @@ mlxsw_sp_neigh_entry_alloc(struct mlxsw_sp *mlxsw_sp, struct neighbour *n, if (!neigh_entry) return NULL;
+ neigh_hold(n); neigh_entry->key.n = n; neigh_entry->rif = rif; INIT_LIST_HEAD(&neigh_entry->nexthop_list); @@ -2172,6 +2173,7 @@ mlxsw_sp_neigh_entry_alloc(struct mlxsw_sp *mlxsw_sp, struct neighbour *n,
static void mlxsw_sp_neigh_entry_free(struct mlxsw_sp_neigh_entry *neigh_entry) { + neigh_release(neigh_entry->key.n); kfree(neigh_entry); }
@@ -4027,6 +4029,8 @@ mlxsw_sp_nexthop_dead_neigh_replace(struct mlxsw_sp *mlxsw_sp, if (err) goto err_neigh_entry_insert;
+ neigh_release(old_n); + read_lock_bh(&n->lock); nud_state = n->nud_state; dead = n->dead; @@ -4035,14 +4039,10 @@ mlxsw_sp_nexthop_dead_neigh_replace(struct mlxsw_sp *mlxsw_sp,
list_for_each_entry(nh, &neigh_entry->nexthop_list, neigh_list_node) { - neigh_release(old_n); - neigh_clone(n); __mlxsw_sp_nexthop_neigh_update(nh, !entry_connected); mlxsw_sp_nexthop_group_refresh(mlxsw_sp, nh->nhgi->nh_grp); }
- neigh_release(n); - return 0;
err_neigh_entry_insert: @@ -4130,6 +4130,11 @@ static int mlxsw_sp_nexthop_neigh_init(struct mlxsw_sp *mlxsw_sp, } }
+ /* Release the reference taken by neigh_lookup() / neigh_create() since + * neigh_entry already holds one. + */ + neigh_release(n); + /* If that is the first nexthop connected to that neigh, add to * nexthop_neighs_list */ @@ -4156,11 +4161,9 @@ static void mlxsw_sp_nexthop_neigh_fini(struct mlxsw_sp *mlxsw_sp, struct mlxsw_sp_nexthop *nh) { struct mlxsw_sp_neigh_entry *neigh_entry = nh->neigh_entry; - struct neighbour *n;
if (!neigh_entry) return; - n = neigh_entry->key.n;
__mlxsw_sp_nexthop_neigh_update(nh, true); list_del(&nh->neigh_list_node); @@ -4174,8 +4177,6 @@ static void mlxsw_sp_nexthop_neigh_fini(struct mlxsw_sp *mlxsw_sp,
if (!neigh_entry->connected && list_empty(&neigh_entry->nexthop_list)) mlxsw_sp_neigh_entry_destroy(mlxsw_sp, neigh_entry); - - neigh_release(n); }
static bool mlxsw_sp_ipip_netdev_ul_up(struct net_device *ol_dev)