Cloudanix VulnDB

CVE-2025-38475

None

CVSS

—

EPSS

0.2%

Published

Jul 28, 2025

CISA due date

—

Cloudanix analysis

Next patch cycle SSVC: Track

A Linux kernel bug can make systems crash when certain network sockets are used with file attribute operations, so updating the kernel removes the risk of unexpected downtime.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Moderate
Impact
Denial Of Service
Component
OS kernel
Class
Memory Corruption
Remediation
Patch
Effort
Medium
Patch risk
Medium

What it actually does

Type confusion between struct smc_sock and struct inet_sock allows inet_opt field to be misinterpreted as a function pointer (clcsk_data_ready), leading to double-free of read-only memory or invalid accesses in cipso_v4_sock_setattr and related netlabel paths when AF_INET/AF_INET6 family is hijacked by SMC sockets.

Why it matters to the business

Linux systems using SMC sockets may experience kernel crashes or denial of service during xattr or security label operations, increasing downtime risk in server and cloud workloads with high kernel dependency counts.

How an attack unfolds

An attacker creates an SMC socket that reuses INET infrastructure, then triggers netlabel or xattr operations that assume inet_sock layout; this causes the kernel to treat a function pointer as inet_opt and attempt to free text-segment memory, resulting in oops or double-free as reported by syzbot and similar to prior SMC variants.

How to fix it

Upgrade Linux kernel to commit 5b02e397929e5b13b969ef1f8e43c7951e2864f5 or later stable releases; rebuild and deploy fixed kernels across affected distributions; avoid prior workarounds that paper over the root cause.

How to confirm the fix worked

Verify kernel build includes inet_sock as first member of smc_sock via pahole; confirm absence of double-free warnings in cipso_v4_sock_setattr after applying the fix; test SMC socket creation followed by xattr operations.

Typical attack path

  1. Create SMC socket with AF_INET family to trigger type confusion
  2. Perform fsetxattr or security label syscall on related inode
  3. Invoke netlbl_sock_setattr or smack_inode_setsecurity path
  4. Trigger cipso_v4_sock_setattr dereference of misinterpreted inet_opt
  5. Cause kvfree_call_rcu double-free or oops in slab code

How to detect it

Search kernel logs for kvfree_call_rcu double-free warnings, cipso_v4_sock_setattr stack traces, or WARNINGs involving smc_sock and inet_opt; inspect crash dumps for addresses matching text segment function pointers.

  • kvfree_call_rcu(): Double-freed call
  • WARNING: CPU:.*at mm/slab_common.c.*kvfree_call_rcu
  • cipso_v4_sock_setattr+0x2f0/0x3f4 net/ipv4/cipso_ipv4.c
  • smack_inode_setsecurity.*security/smack/smack_lsm.c

What your security team should do

  • Prioritize kernel upgrade to fixed commit within standard patch cycles given low EPSS
  • Monitor for related kernel oops in production SMC workloads
  • Audit custom SMC usage and disable if not required
  • Track downstream package updates for affected distributions

The record

In the Linux kernel, the following vulnerability has been resolved: smc: Fix various oops due to inet_sock type confusion. syzbot reported weird splats [0][1] in cipso_v4_sock_setattr() while freeing inet_sk(sk)->inet_opt. The address was freed multiple times even though it was read-only memory. cipso_v4_sock_setattr() did nothing wrong, and the root cause was type confusion. The cited commit made it possible to create smc_sock as an INET socket. The issue is that struct smc_sock does not have struct inet_sock as the first member but hijacks AF_INET and AF_INET6 sk_family, which confuses various places. In this case, inet_sock.inet_opt was actually smc_sock.clcsk_data_ready(), which is an address of a function in the text segment. $ pahole -C inet_sock vmlinux struct inet_sock { ... struct ip_options_rcu * inet_opt; /* 784 8 */ $ pahole -C smc_sock vmlinux struct smc_sock { ... void (*clcsk_data_ready)(struct sock *); /* 784 8 */ The same issue for another field was reported before. [2][3] At that time, an ugly hack was suggested [4], but it makes both INET and SMC code error-prone and hard to change. Also, yet another variant was fixed by a hacky commit 98d4435efcbf3 ("net/smc: prevent NULL pointer dereference in txopt_get"). Instead of papering over the root cause by such hacks, we should not allow non-INET socket to reuse the INET infra. Let's add inet_sock as the first member of smc_sock. [0]: kvfree_call_rcu(): Double-freed call. rcu_head 000000006921da73 WARNING: CPU: 0 PID: 6718 at mm/slab_common.c:1956 kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955 Modules linked in: CPU: 0 UID: 0 PID: 6718 Comm: syz.0.17 Tainted: G W 6.16.0-rc4-syzkaller-g7482bb149b9f #0 PREEMPT Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955 lr : kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955 sp : ffff8000a03a7730 x29: ffff8000a03a7730 x28: 00000000fffffff5 x27: 1fffe000184823d3 x26: dfff800000000000 x25: ffff0000c2411e9e x24: ffff0000dd88da00 x23: ffff8000891ac9a0 x22: 00000000ffffffea x21: ffff8000891ac9a0 x20: ffff8000891ac9a0 x19: ffff80008afc2480 x18: 00000000ffffffff x17: 0000000000000000 x16: ffff80008ae642c8 x15: ffff700011ede14c x14: 1ffff00011ede14c x13: 0000000000000004 x12: ffffffffffffffff x11: ffff700011ede14c x10: 0000000000ff0100 x9 : 5fa3c1ffaf0ff000 x8 : 5fa3c1ffaf0ff000 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff8000a03a7078 x4 : ffff80008f766c20 x3 : ffff80008054d360 x2 : 0000000000000000 x1 : 0000000000000201 x0 : 0000000000000000 Call trace: kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955 (P) cipso_v4_sock_setattr+0x2f0/0x3f4 net/ipv4/cipso_ipv4.c:1914 netlbl_sock_setattr+0x240/0x334 net/netlabel/netlabel_kapi.c:1000 smack_netlbl_add+0xa8/0x158 security/smack/smack_lsm.c:2581 smack_inode_setsecurity+0x378/0x430 security/smack/smack_lsm.c:2912 security_inode_setsecurity+0x118/0x3c0 security/security.c:2706 __vfs_setxattr_noperm+0x174/0x5c4 fs/xattr.c:251 __vfs_setxattr_locked+0x1ec/0x218 fs/xattr.c:295 vfs_setxattr+0x158/0x2ac fs/xattr.c:321 do_setxattr fs/xattr.c:636 [inline] file_setxattr+0x1b8/0x294 fs/xattr.c:646 path_setxattrat+0x2ac/0x320 fs/xattr.c:711 __do_sys_fsetxattr fs/xattr.c:761 [inline] __se_sys_fsetxattr fs/xattr.c:758 [inline] __arm64_sys_fsetxattr+0xc0/0xdc fs/xattr.c:758 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 [ ---truncated---

Affected packages

Ecosystem Package Introduced Fixed
Debian:13 linux 0 6.12.41-1
Debian:14 linux 0 No fix
Debian:14 linux 0 6.16.3-1
Linux Kernel 6.11.0 6.12.40
SUSE:Linux Enterprise Live Patching 15 SP7 kernel-livepatch-SLE15-SP7-RT_Update_3 0 1-150700.1.5.1
SUSE:Real Time Module 15 SP7 kernel-rt 0 6.4.0-150700.7.13.1
SUSE:Real Time Module 15 SP7 kernel-source-rt 0 6.4.0-150700.7.13.1
SUSE:Real Time Module 15 SP7 kernel-syms-rt 0 6.4.0-150700.7.13.1
openSUSE:Leap 16.0 dtb-aarch64 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-64kb 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-default 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-default-base 0 6.12.0-160000.6.1.160000.2.4
openSUSE:Leap 16.0 kernel-docs 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-kvmsmall 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-obs-build 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-obs-qa 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-rt 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-source 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-syms 0 6.12.0-160000.6.1
openSUSE:Leap 16.0 kernel-zfcpdump 0 6.12.0-160000.6.1

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