CVE-2025-38459 in Linux
Summary
by MITRE • 07/25/2025
In the Linux kernel, the following vulnerability has been resolved:
atm: clip: Fix infinite recursive call of clip_push().
syzbot reported the splat below. [0]
This happens if we call ioctl(ATMARP_MKIP) more than once.
During the first call, clip_mkip() sets clip_push() to vcc->push(), and the second call copies it to clip_vcc->old_push().
Later, when the socket is close()d, vcc_destroy_socket() passes NULL skb to clip_push(), which calls clip_vcc->old_push(), triggering the infinite recursion.
Let's prevent the second ioctl(ATMARP_MKIP) by checking vcc->user_back, which is allocated by the first call as clip_vcc.
Note also that we use lock_sock() to prevent racy calls.
[0]:
BUG: TASK stack guard page was hit at ffffc9000d66fff8 (stack is ffffc9000d670000..ffffc9000d678000) Oops: stack guard page: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5322 Comm: syz.0.0 Not tainted 6.16.0-rc4-syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:clip_push+0x5/0x720 net/atm/clip.c:191 Code: e0 8f aa 8c e8 1c ad 5b fa eb ae 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 <41> 57 41 56 41 55 41 54 53 48 83 ec 20 48 89 f3 49 89 fd 48 bd 00 RSP: 0018:ffffc9000d670000 EFLAGS: 00010246 RAX: 1ffff1100235a4a5 RBX: ffff888011ad2508 RCX: ffff8880003c0000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888037f01000 RBP: dffffc0000000000 R08: ffffffff8fa104f7 R09: 1ffffffff1f4209e R10: dffffc0000000000 R11: ffffffff8a99b300 R12: ffffffff8a99b300 R13: ffff888037f01000 R14: ffff888011ad2500 R15: ffff888037f01578 FS: 000055557ab6d500(0000) GS:ffff88808d250000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffc9000d66fff8 CR3: 0000000043172000 CR4: 0000000000352ef0 Call Trace: <TASK> clip_push+0x6dc/0x720 net/atm/clip.c:200 clip_push+0x6dc/0x720 net/atm/clip.c:200 clip_push+0x6dc/0x720 net/atm/clip.c:200 ... clip_push+0x6dc/0x720 net/atm/clip.c:200 clip_push+0x6dc/0x720 net/atm/clip.c:200 clip_push+0x6dc/0x720 net/atm/clip.c:200 vcc_destroy_socket net/atm/common.c:183 [inline]
vcc_release+0x157/0x460 net/atm/common.c:205 __sock_release net/socket.c:647 [inline]
sock_close+0xc0/0x240 net/socket.c:1391 __fput+0x449/0xa70 fs/file_table.c:465 task_work_run+0x1d1/0x260 kernel/task_work.c:227 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:114 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ff31c98e929 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fffb5aa1f78 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 0000000000012747 RCX: 00007ff31c98e929 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007ff31cbb7ba0 R08: 0000000000000001 R09: 0000000db5aa226f R10: 00007ff31c7ff030 R11: 0000000000000246 R12: 00007ff31cbb608c R13: 00007ff31cbb6080 R14: ffffffffffffffff R15: 00007fffb5aa2090 </TASK> Modules linked in:
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Analysis
by VulDB Data Team • 01/04/2026
The vulnerability identified as CVE-2025-38459 resides within the Linux kernel's ATM (Asynchronous Transfer Mode) subsystem, specifically in the CLIP (Classical IP over ATM) implementation. This flaw manifests as an infinite recursive call to the clip_push() function, which arises from improper handling of the ioctl(ATMARP_MKIP) command when invoked multiple times on the same ATM virtual circuit. The root cause stems from the sequence of operations during the first ioctl call, where clip_mkip() assigns clip_push() to vcc->push(), and subsequent calls copy this value to clip_vcc->old_push(). When the socket is closed, vcc_destroy_socket() passes a NULL skb to clip_push(), which then recursively calls clip_vcc->old_push(), resulting in a stack overflow and system crash.
The technical mechanism of exploitation involves a race condition and improper state management within the ATM subsystem. The vulnerability is categorized under CWE-674, which deals with Uncontrolled Recursion, and aligns with ATT&CK technique T1059.008 for Execution through Command and Script Interpreters. The recursive call chain begins with clip_push() being invoked with a NULL skb, which triggers a call to the stored old_push function, leading to an infinite loop that eventually exhausts the kernel stack space. The stack guard page violation at ffffc9000d66fff8 confirms this stack overflow condition, as evidenced by the kernel oops message and the repetitive call trace showing clip_push calling itself indefinitely.
The operational impact of this vulnerability is significant, as it can lead to a complete system crash or denial of service in systems running Linux kernels with ATM support. This affects any system that utilizes ATM networking capabilities, particularly those implementing CLIP for IP packet transmission over ATM networks. The vulnerability is particularly concerning because it can be triggered through a single process performing multiple ioctl operations, making it exploitable by local users or potentially by malicious actors who can access ATM network interfaces. The fix implemented by checking vcc->user_back prevents the second ioctl call from overwriting the existing push handler, thus breaking the recursive call cycle. Additionally, the use of lock_sock() ensures proper synchronization between concurrent calls, preventing race conditions that could otherwise lead to similar issues. This patch demonstrates the importance of proper state management and defensive programming in kernel space, where recursive calls must be carefully controlled to prevent stack exhaustion. The vulnerability highlights the critical need for robust input validation and state tracking in kernel modules, especially those handling network protocols where improper state transitions can lead to system instability. The fix maintains the original functionality while preventing the dangerous recursion, aligning with the principle of least privilege and minimal attack surface in kernel security design.