Hi,
I'm getting a KASAN (use after free) error when doing:
ip link add vxlan1 type vxlan external
ip link set vxlan1 up
ip link set vxlan1 down
ip link del vxlan1
[ 600.495331]
==================================================================
[ 600.509678] BUG: KASAN: use-after-free in vxlan_dellink+0x33d/0x390 [vxlan]
[ 600.523083] Write of size 8 at addr ffff88056ce54018 by task ip/16216
[ 600.542239] CPU: 12 PID: 16216 Comm: ip Not tainted 4.12.0-rc2 #24
[ 600.554442] Hardware name: HP ProLiant DL380p Gen8, BIOS P70 08/02/2014
[ 600.567013] Call Trace:
[ 600.574742] dump_stack+0x63/0x89
[ 600.583458] print_address_description+0x78/0x290
[ 600.593612] kasan_report+0x257/0x370
[ 600.602857] ? vxlan_dellink+0x33d/0x390 [vxlan]
[ 600.612765] __asan_report_store8_noabort+0x1c/0x20
[ 600.622937] vxlan_dellink+0x33d/0x390 [vxlan]
[ 600.632636] rtnl_delete_link+0xb9/0x110
[ 600.641542] ? rtnl_af_register+0xc0/0xc0
[ 600.650898] ? nla_parse+0x36/0x260
[ 600.659558] rtnl_dellink+0x1fb/0x780
[ 600.668350] ? unwind_dump+0x360/0x360
[ 600.676802] ? rtnl_bridge_getlink+0x620/0x620
[ 600.686036] ? __module_text_address+0x18/0x150
[ 600.695300] ? ns_capable_common+0xd4/0x110
[ 600.704157] ? sock_sendmsg+0xba/0xf0
[ 600.712264] ? ns_capable+0x13/0x20
[ 600.720201] ? __netlink_ns_capable+0xcc/0x100
[ 600.729131] rtnetlink_rcv_msg+0x255/0x6c0
[ 600.737464] ? rtnl_newlink+0x1640/0x1640
[ 600.745604] ? __read_once_size_nocheck.constprop.7+0x20/0x20
[ 600.755882] ? __read_once_size_nocheck.constprop.7+0x20/0x20
[ 600.765963] ? memset+0x31/0x40
[ 600.772985] netlink_rcv_skb+0x2de/0x460
[ 600.780829] ? rtnl_newlink+0x1640/0x1640
[ 600.788755] ? netlink_ack+0xaf0/0xaf0
[ 600.796181] ? __kmalloc_node_track_caller+0x205/0x2d0
[ 600.805370] ? __alloc_skb+0xdd/0x580
[ 600.812646] rtnetlink_rcv+0x28/0x30
[ 600.819882] netlink_unicast+0x430/0x620
[ 600.827433] ? netlink_attachskb+0x660/0x660
[ 600.835211] ? rw_copy_check_uvector+0x90/0x290
[ 600.843097] ? __module_text_address+0x18/0x150
[ 600.850985] netlink_sendmsg+0x7df/0xb90
[ 600.858105] ? netlink_unicast+0x620/0x620
[ 600.865493] ? kasan_alloc_pages+0x38/0x40
[ 600.873060] ? netlink_unicast+0x620/0x620
[ 600.880458] sock_sendmsg+0xba/0xf0
[ 600.886784] ___sys_sendmsg+0x6c9/0x8e0
[ 600.893300] ? copy_msghdr_from_user+0x520/0x520
[ 600.901017] ? memcg_write_event_control+0xd50/0xd50
[ 600.908938] ? __alloc_pages_slowpath+0x1ef0/0x1ef0
[ 600.916082] ? mem_cgroup_commit_charge+0xc4/0x1420
[ 600.923049] ? lru_cache_add_active_or_unevictable+0x7d/0x1a0
[ 600.931943] ? __handle_mm_fault+0x1bfe/0x2ba0
[ 600.939255] ? __pmd_alloc+0x240/0x240
[ 600.944767] __sys_sendmsg+0xce/0x160
[ 600.950154] ? __sys_sendmsg+0xce/0x160
[ 600.956030] ? SyS_shutdown+0x190/0x190
[ 600.962546] ? mntput+0x57/0x70
[ 600.968576] ? __fput+0x429/0x730
[ 600.973526] ? handle_mm_fault+0x28a/0x650
[ 600.979844] ? find_vma+0x1f/0x160
[ 600.985801] SyS_sendmsg+0x12/0x20
[ 600.991857] entry_SYSCALL_64_fastpath+0x1a/0xa5
[ 600.999044] RIP: 0033:0x7fe11cd80037
[ 601.005021] RSP: 002b:00007ffe0e7fc738 EFLAGS: 00000246 ORIG_RAX:
000000000000002e
[ 601.014890] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fe11cd80037
[ 601.024808] RDX: 0000000000000000 RSI: 00007ffe0e7fc780 RDI: 0000000000000003
[ 601.035392] RBP: 00007ffe0e7fc780 R08: 0000000000000001 R09: fefefeff77686d74
[ 601.045517] R10: 00000000000005eb R11: 0000000000000246 R12: 00007ffe0e7fc7c0
[ 601.055590] R13: 0000000000669400 R14: 00007ffe0e804830 R15: 0000000000000000
[ 601.069998] The buggy address belongs to the page:
[ 601.078182] page:ffffea0015b39500 count:0 mapcount:-127 mapping:
(null) index:0x0
[ 601.089760] flags: 0x2fffff80000000()
[ 601.096304] raw: 002fffff80000000 0000000000000000 0000000000000000
00000000ffffff80
[ 601.107417] raw: ffffea00156b2020 ffffea001836cb20 0000000000000002
0000000000000000
[ 601.118699] page dumped because: kasan: bad access detected
[ 601.131352] Memory state around the buggy address:
[ 601.139488] ffff88056ce53f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00
[ 601.149179] ffff88056ce53f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00
[ 601.159941] >ffff88056ce54000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ff
[ 601.170313] ^
[ 601.176429] ffff88056ce54080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ff
[ 601.187098] ffff88056ce54100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ff
[ 601.196978]
==================================================================
The flow is something like this:
When we are upping the interface, we are calling vxlan_open() and after
creating the
sockets (v4 & v6) we call vxlan_vs_add_dev() and add the vxlan device to each
socket's list.
When we put down the interface, we call vxlan_stop() -> vxlan_sock_release()
there
after calling __vxlan_sock_release_prep() we free each socket, the issue is
that the vxlan
device is still part of each socket's list.
When we delete the vxlan interface, vxlan_dellink() is called and there we do:
hlist_del_rcu(&vxlan->hlist), which access already freed memory.
I'm not too familiar with the vxlan module, so to me a trivial fix like this
makes sense.
Am I missing something?
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 328b471..7d57faf 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1058,6 +1058,7 @@ static bool __vxlan_sock_release_prep(struct vxlan_sock
*vs)
static void vxlan_sock_release(struct vxlan_dev *vxlan)
{
struct vxlan_sock *sock4 = rtnl_dereference(vxlan->vn4_sock);
+ struct vxlan_net *vn = net_generic(vxlan->net, vxlan_net_id);
#if IS_ENABLED(CONFIG_IPV6)
struct vxlan_sock *sock6 = rtnl_dereference(vxlan->vn6_sock);
@@ -1067,6 +1068,10 @@ static void vxlan_sock_release(struct vxlan_dev *vxlan)
rcu_assign_pointer(vxlan->vn4_sock, NULL);
synchronize_net();
+ spin_lock(&vn->sock_lock);
+ hlist_del_rcu(&vxlan->hlist);
+ spin_unlock(&vn->sock_lock);
+
if (__vxlan_sock_release_prep(sock4)) {
udp_tunnel_sock_release(sock4->sock);
kfree(sock4);
@@ -3286,15 +3291,9 @@ static int vxlan_changelink(struct net_device *dev,
struct nlattr *tb[],
static void vxlan_dellink(struct net_device *dev, struct list_head *head)
{
struct vxlan_dev *vxlan = netdev_priv(dev);
- struct vxlan_net *vn = net_generic(vxlan->net, vxlan_net_id);
vxlan_flush(vxlan, true);
- spin_lock(&vn->sock_lock);
- if (!hlist_unhashed(&vxlan->hlist))
- hlist_del_rcu(&vxlan->hlist);
- spin_unlock(&vn->sock_lock);
-
gro_cells_destroy(&vxlan->gro_cells);
list_del(&vxlan->next);
unregister_netdevice_queue(dev, head);
Mark
