Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
gtp: Suppress list corruption splat in gtp_net_exit_batch_rtnl().
Brad Spengler reported the list_del() corruption splat in gtp_net_exit_batch_rtnl(). [0]
Commit eb28fd76c0a0 (“gtp: Destroy device along with udp socket’s netns dismantle.”) added the for_each_netdev() loop in gtp_net_exit_batch_rtnl() to destroy devices in each netns as done in geneve and ip tunnels.
However, this could trigger ->dellink() twice for the same device during ->exit_batch_rtnl().
Say we have two netns A & B and gtp device B that resides in netns B but whose UDP socket is in netns A.
-
cleanup_net() processes netns A and then B.
-
gtp_net_exit_batch_rtnl() finds the device B while iterating netns A’s gn->gtp_dev_list and calls ->dellink().
[ device B is not yet unlinked from netns B as unregister_netdevice_many() has not been called. ]
- gtp_net_exit_batch_rtnl() finds the device B while iterating netns B’s for_each_netdev() and calls ->dellink().
gtp_dellink() cleans up the device’s hash table, unlinks the dev from gn->gtp_dev_list, and calls unregister_netdevice_queue().
Basically, calling gtp_dellink() multiple times is fine unless CONFIG_DEBUG_LIST is enabled.
Let’s remove for_each_netdev() in gtp_net_exit_batch_rtnl() and delegate the destruction to default_device_exit_batch() as done in bareudp.
[0]:
list_del corruption, ffff8880aaa62c00->next (autoslab_size_M_dev_P_net_core_dev_11127_8_1328_8_S_4096_A_64_n_139+0xc00/0x1000 [slab object]) is LIST_POISON1 (ffffffffffffff02) (prev is 0xffffffffffffff04)
kernel BUG at lib/list_debug.c:58!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 UID: 0 PID: 1804 Comm: kworker/u8:7 Tainted: G T 6.12.13-grsec-full-20250211091339 #1
Tainted: [T]=RANDSTRUCT
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: netns cleanup_net
RIP: 0010:[
Details
- Affected product:
- Ubuntu 18.04 ELS
- Affected packages:
- linux @ 4.15.0
In the Linux kernel, the following vulnerability has been resolved:
gtp: Suppress list corruption splat in gtp_net_exit_batch_rtnl().
Brad Spengler reported the list_del() corruption splat in gtp_net_exit_batch_rtnl(). [0]
Commit eb28fd76c0a0 (“gtp: Destroy device along with udp socket’s netns dismantle.”) added the for_each_netdev() loop in gtp_net_exit_batch_rtnl() to destroy devices in each netns as done in geneve and ip tunnels.
However, this could trigger ->dellink() twice for the same device during ->exit_batch_rtnl().
Say we have two netns A & B and gtp device B that resides in netns B but whose UDP socket is in netns A.
-
cleanup_net() processes netns A and then B.
-
gtp_net_exit_batch_rtnl() finds the device B while iterating netns A’s gn->gtp_dev_list and calls ->dellink().
[ device B is not yet unlinked from netns B as unregister_netdevice_many() has not been called. ]
- gtp_net_exit_batch_rtnl() finds the device B while iterating netns B’s for_each_netdev() and calls ->dellink().
gtp_dellink() cleans up the device’s hash table, unlinks the dev from gn->gtp_dev_list, and calls unregister_netdevice_queue().
Basically, calling gtp_dellink() multiple times is fine unless CONFIG_DEBUG_LIST is enabled.
Let’s remove for_each_netdev() in gtp_net_exit_batch_rtnl() and delegate the destruction to default_device_exit_batch() as done in bareudp.
[0]:
list_del corruption, ffff8880aaa62c00->next (autoslab_size_M_dev_P_net_core_dev_11127_8_1328_8_S_4096_A_64_n_139+0xc00/0x1000 [slab object]) is LIST_POISON1 (ffffffffffffff02) (prev is 0xffffffffffffff04)
kernel BUG at lib/list_debug.c:58!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 UID: 0 PID: 1804 Comm: kworker/u8:7 Tainted: G T 6.12.13-grsec-full-20250211091339 #1
Tainted: [T]=RANDSTRUCT
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: netns cleanup_net
RIP: 0010:[