CVE: CVE-2025-21865
Published: 2025-03-12
Description: 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.

  1. cleanup_net() processes netns A and then B.

  2. 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. ]

  3. 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[PII_REDACTED]1339 #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:[<ffffffff84947381>] __list_del_entry_valid_or_report+0x141/0x200 lib/list_debug.c:58
Code: c2 76 91 31 c0 e8 9f b1 f7 fc 0f 0b 4d 89 f0 48 c7 c1 02 ff ff ff 48 89 ea 48 89 ee 48 c7 c7 e0 c2 76 91 31 c0 e8 7f b1 f7 fc <0f> 0b 4d 89 e8 48 c7 c1 04 ff ff ff 48 89 ea 48 89 ee 48 c7 c7 60
RSP: 0018:fffffe8040b4fbd0 EFLAGS: 00010283
RAX:[PII_REDACTED]0000cc RBX: dffffc[PII_REDACTED] RCX: ffffffff818c4054
RDX: ffffffff84947381 RSI: ffffffff818d1512 RDI: [PII_REDACTED]
RBP: ffff8880aaa62c00 R08: [PII_REDACTED] R09: fffffbd008169f32
R10: fffffe8040b4f997 R11: [PII_REDACTED] R12: a1988d84f24943e4
R13: ffffffffffffff02 R14: ffffffffffffff04 R15: ffff8880aaa62c08
RBX: kasan shadow of 0x0
RCX: __wake_up_klogd.part.0+0x74/0xe0 kernel/printk/printk.c:4554
RDX: __list_del_entry_valid_or_report+0x141/0x200 lib/list_debug.c:58
RSI: vprintk+0x72/0x100 kernel/printk/printk_safe.c:71
RBP: autoslab_size_M_dev_P_net_core_dev_11127_8_1328_8_S_4096_A_64_n_139+0xc00/0x1000 [slab object]
RSP: process kstack fffffe8040b4fbd0+0x7bd0/0x8000 [kworker/u8:7+netns 1804 ]
R09: kasan shadow of process kstack fffffe8040b4f990+0x7990/0x8000 [kworker/u8:7+netns 1804 ]
R10: process kstack fffffe8040b4f997+0x7997/0x8000 [kworker/u8:7+netns 1804 ]
R15: autoslab_size_M_dev_P_net_core_dev_11127_8_1328_8_S_4096_A_64_n_139+0xc08/0x1000 [slab object]
FS:  [PII_REDACTED](0000) GS:ffff[PII_REDACTED]00(0000) knlGS:[PII_REDACTED]
CS:  0010 DS: 0000 ES: 0000 CR0: [PII_REDACTED]
CR2: 0000748f5372c000 CR3: [PII_REDACTED] CR4:[PII_REDACTED]3406f0 shadow CR4:[PII_REDACTED]3406f0
Stack:
 [PII_REDACTED] ffffffff8a0c35e7 ffffffff8a0c3603 ffff8880aaa62c00
 ffff8880aaa62c00 [PII_REDACTED] ffff[PII_REDACTED]1c [PII_REDACTED]
 [PII_REDACTED] ffff8880aaa62000 fffffe8040b4fd40 ffffffff8a0c360d
Call Trace:
 <TASK>
 [<ffffffff8a0c360d>] __list_del_entry_valid include/linux/list.h:131 [inline] fffffe8040b4fc28
 [<ffffffff8a0c360d>] __list_del_entry include/linux/list.h:248 [inline] fffffe8040b4fc28
 [<ffffffff8a0c360d>] list_del include/linux/list.h:262 [inl
---truncated---
CVSS Score: 5.5 (MEDIUM)
CWE: CWE-787, CWE-787
References: https://git.kernel.org/stable/c/33eb925c0c26e86ca540a[PII_REDACTED]2bf911f22; https://git.kernel.org/stable/c/37e7644b961600ef0beb01d3970c3034a62913af; https://git.kernel.org/stable/c/4ccacf86491d33d2486b62d4d44864d7101b299d