CVE-2023-54142 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
gtp: Fix use-after-free in __gtp_encap_destroy().
syzkaller reported use-after-free in __gtp_encap_destroy(). [0]
It shows the same process freed sk and touched it illegally.
Commit e198987e7dd7 ("gtp: fix suspicious RCU usage") added lock_sock() and release_sock() in __gtp_encap_destroy() to protect sk->sk_user_data, but release_sock() is called after sock_put() releases the last refcnt.
[0]:
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:541 [inline]
BUG: KASAN: slab-use-after-free in queued_spin_lock include/asm-generic/qspinlock.h:111 [inline]
BUG: KASAN: slab-use-after-free in do_raw_spin_lock include/linux/spinlock.h:186 [inline]
BUG: KASAN: slab-use-after-free in __raw_spin_lock_bh include/linux/spinlock_api_smp.h:127 [inline]
BUG: KASAN: slab-use-after-free in _raw_spin_lock_bh+0x75/0xe0 kernel/locking/spinlock.c:178 Write of size 4 at addr ffff88800dbef398 by task syz-executor.2/2401
CPU: 1 PID: 2401 Comm: syz-executor.2 Not tainted 6.4.0-rc5-01219-gfa0e21fa4443 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x72/0xa0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:351 [inline]
print_report+0xcc/0x620 mm/kasan/report.c:462 kasan_report+0xb2/0xe0 mm/kasan/report.c:572 check_region_inline mm/kasan/generic.c:181 [inline]
kasan_check_range+0x39/0x1c0 mm/kasan/generic.c:187 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:541 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:111 [inline]
do_raw_spin_lock include/linux/spinlock.h:186 [inline]
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:127 [inline]
_raw_spin_lock_bh+0x75/0xe0 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:355 [inline]
release_sock+0x1f/0x1a0 net/core/sock.c:3526 gtp_encap_disable_sock drivers/net/gtp.c:651 [inline]
gtp_encap_disable+0xb9/0x220 drivers/net/gtp.c:664 gtp_dev_uninit+0x19/0x50 drivers/net/gtp.c:728 unregister_netdevice_many_notify+0x97e/0x1520 net/core/dev.c:10841 rtnl_delete_link net/core/rtnetlink.c:3216 [inline]
rtnl_dellink+0x3c0/0xb30 net/core/rtnetlink.c:3268 rtnetlink_rcv_msg+0x450/0xb10 net/core/rtnetlink.c:6423 netlink_rcv_skb+0x15d/0x450 net/netlink/af_netlink.c:2548 netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
netlink_unicast+0x700/0x930 net/netlink/af_netlink.c:1365 netlink_sendmsg+0x91c/0xe30 net/netlink/af_netlink.c:1913 sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg+0x1b7/0x200 net/socket.c:747 ____sys_sendmsg+0x75a/0x990 net/socket.c:2493 ___sys_sendmsg+0x11d/0x1c0 net/socket.c:2547 __sys_sendmsg+0xfe/0x1d0 net/socket.c:2576 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3f/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x72/0xdc RIP: 0033:0x7f1168b1fe5d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 73 9f 1b 00 f7 d8 64 89 01 48 RSP: 002b:00007f1167edccc8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00000000004bbf80 RCX: 00007f1168b1fe5d RDX: 0000000000000000 RSI: 00000000200002c0 RDI: 0000000000000003 RBP: 00000000004bbf80 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000000000b R14: 00007f1168b80530 R15: 0000000000000000 </TASK>
Allocated by task 1483: kasan_save_stack+0x22/0x50 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 __kasan_slab_alloc+0x ---truncated---
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Analysis
by VulDB Data Team • 01/03/2026
The vulnerability identified as CVE-2023-54142 resides within the Linux kernel's GTP (GPRS Tunneling Protocol) implementation, specifically in the `__gtp_encap_destroy()` function. This flaw manifests as a use-after-free error, a critical class of memory safety issue that can lead to system instability, privilege escalation, or arbitrary code execution. The vulnerability was detected by the syzkaller automated fuzzing framework, which reported that a process attempted to access a socket structure (`sk`) after it had been freed, indicating a classic race condition or improper resource management. The underlying issue stems from the improper sequencing of socket reference counting and locking operations during the destruction of GTP encapsulation sockets.
The root cause of this vulnerability can be traced to a commit e198987e7dd7 titled "gtp: fix suspicious RCU usage," which introduced `lock_sock()` and `release_sock()` calls to protect access to `sk->sk_user_data`. However, this change introduced a flaw in the order of operations where `release_sock()` is invoked after `sock_put()`, which decrements the socket reference count and effectively frees the socket structure. This improper sequence results in a situation where the socket structure is freed, but subsequent operations attempt to access it, leading to a use-after-free condition. The kernel address sanitizer (KASAN) stack trace confirms this behavior, showing the access violation occurring within `instrument_atomic_read_write` and related spinlock functions, highlighting the memory corruption that occurs when the freed socket structure is accessed after being released.
The operational impact of this vulnerability is significant, as it can be exploited by malicious actors to gain unauthorized access to system resources or compromise the integrity of the kernel. The GTP protocol is commonly used in mobile network infrastructure for tunneling user data between network elements, making this vulnerability particularly concerning in environments where such protocols are actively utilized. The vulnerability allows for potential privilege escalation or denial-of-service conditions, depending on how the exploitation is carried out. According to CWE-416, this corresponds to the use of freed memory, a well-known vulnerability pattern that has been extensively documented in the context of kernel exploitation and security research.
Mitigation strategies for CVE-2023-54142 should focus on correcting the ordering of socket operations within the `__gtp_encap_destroy()` function. The recommended fix involves ensuring that `release_sock()` is called before `sock_put()`, or alternatively, that proper synchronization mechanisms are in place to prevent access to a socket after it has been marked for destruction. This aligns with ATT&CK technique T1068, which involves exploiting vulnerabilities in the kernel to escalate privileges. System administrators should prioritize applying the patched kernel version that resolves this issue, as the vulnerability is exploitable in the context of kernel-level memory management flaws. Additionally, monitoring for unusual socket destruction patterns and implementing proper memory access controls can help detect potential exploitation attempts. The fix should also be validated through comprehensive testing to ensure that it does not introduce regressions in the GTP functionality or affect other socket operations within the kernel.