From: Ido Schimmel <idosch@nvidia.com> stable inclusion from stable-v5.10.248 commit a2dfe6758fc63e542105bee8b17a3a7485684db0 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/13354 CVE: CVE-2025-68801 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ 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> Signed-off-by: Cai Xinchen <caixinchen1@huawei.com> --- .../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 d2887ae508bb..e22ee1336d74 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c @@ -2032,6 +2032,7 @@ 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); @@ -2041,6 +2042,7 @@ 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); } @@ -3607,6 +3609,8 @@ 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; @@ -3615,14 +3619,10 @@ 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->nh_grp); } - neigh_release(n); - return 0; err_neigh_entry_insert: @@ -3711,6 +3711,11 @@ 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 */ @@ -3737,11 +3742,9 @@ 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); @@ -3755,8 +3758,6 @@ 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) -- 2.34.1