UBUNTU-CVE-2025-21812: XEE
In the Linux kernel, the following vulnerability has been resolved: ax25: rcu protect dev->ax25ptr syzbot found a lockdep issue [1]. We should remove ax25 RTNL dependency in ax25setsockopt() This should also fix a variety of possible UAF in ax25. [1] WARNING: possible circular locking dependency detected 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Not tainted ------------------------------------------------------ syz.5.1818/12806 is trying to acquire lock: ffffffff8fcb3988 (rtnlmutex){+.+.}-{4:4}, at: ax25setsockopt+0xa55/0xe90 net/ax25/afax25.c:680 but task is already holding lock: ffff8880617ac258 (sklock-AFAX25){+.+.}-{0:0}, at: locksock include/net/sock.h:1618 [inline] ffff8880617ac258 (sklock-AFAX25){+.+.}-{0:0}, at: ax25setsockopt+0x209/0xe90 net/ax25/afax25.c:574 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (sklock-AFAX25){+.+.}-{0:0}: lockacquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 locksocknested+0x48/0x100 net/core/sock.c:3642 locksock include/net/sock.h:1618 [inline] ax25killbydevice net/ax25/afax25.c:101 [inline] ax25deviceevent+0x24d/0x580 net/ax25/afax25.c:146 notifiercallchain+0x1a5/0x3f0 kernel/notifier.c:85 devnotifyflags+0x207/0x400 devchangeflags+0xf0/0x1a0 net/core/dev.c:9026 devifsioc+0x7c8/0xe70 net/core/devioctl.c:563 devioctl+0x719/0x1340 net/core/devioctl.c:820 sockdoioctl+0x240/0x460 net/socket.c:1234 sockioctl+0x626/0x8e0 net/socket.c:1339 vfsioctl fs/ioctl.c:51 [inline] dosysioctl fs/ioctl.c:906 [inline] sesysioctl+0xf5/0x170 fs/ioctl.c:892 dosyscallx64 arch/x86/entry/common.c:52 [inline] dosyscall64+0xf3/0x230 arch/x86/entry/common.c:83 entrySYSCALL64afterhwframe+0x77/0x7f -> #0 (rtnlmutex){+.+.}-{4:4}: checkprevadd kernel/locking/lockdep.c:3161 [inline] checkprevsadd kernel/locking/lockdep.c:3280 [inline] validatechain+0x18ef/0x5920 kernel/locking/lockdep.c:3904 lockacquire+0x1397/0x2100 kernel/locking/lockdep.c:5226 lockacquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 mutexlockcommon kernel/locking/mutex.c:585 [inline] mutexlock+0x1ac/0xee0 kernel/locking/mutex.c:735 ax25setsockopt+0xa55/0xe90 net/ax25/afax25.c:680 dosocksetsockopt+0x3af/0x720 net/socket.c:2324 syssetsockopt net/socket.c:2349 [inline] dosyssetsockopt net/socket.c:2355 [inline] sesyssetsockopt net/socket.c:2352 [inline] x64syssetsockopt+0x1ee/0x280 net/socket.c:2352 dosyscallx64 arch/x86/entry/common.c:52 [inline] dosyscall64+0xf3/0x230 arch/x86/entry/common.c:83 entrySYSCALL64afterhwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sklock-AFAX25); lock(rtnlmutex); lock(sklock-AFAX25); lock(rtnlmutex); DEADLOCK 1 lock held by syz.5.1818/12806: #0: ffff8880617ac258 (sklock-AFAX25){+.+.}-{0:0}, at: locksock include/net/sock.h:1618 [inline] #0: ffff8880617ac258 (sklock-AFAX25){+.+.}-{0:0}, at: ax25setsockopt+0x209/0xe90 net/ax25/afax25.c:574 stack backtrace: CPU: 1 UID: 0 PID: 12806 Comm: syz.5.1818 Not tainted 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Call Trace: <TASK> dumpstack lib/dumpstack.c:94 [inline] dumpstacklvl+0x241/0x360 lib/dumpstack.c:120 printcircularbug+0x13a/0x1b0 kernel/locking/lockdep.c:2074 checknoncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206 checkprevadd kernel/locking/lockdep.c:3161 [inline] checkprevsadd kernel/lockin ---truncated---
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1119.126~20.04.1 - Upgrade
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ubuntu/linux-azure-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1125.134~20.04.1 - Upgrade
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ubuntu/linux-azure-fde-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1124.133~20.04.1 - Upgrade
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ubuntu/linux-gcp-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1120.130~20.04.1 - Upgrade
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ubuntu/linux-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-202.212~20.04.1 - Upgrade
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ubuntu/linux-ibm-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1113.117~20.04.1 - Upgrade
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ubuntu/linux-intel-iotg-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1114.120~20.04.1 - Upgrade
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ubuntu/linux-lowlatency-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-197.207~20.04.1 - Upgrade
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ubuntu/linux-nvidia-tegra-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1070.72~20.04.1 - Upgrade
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ubuntu/linux-oracle-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1116.122~20.04.1 - Upgrade
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ubuntu/linux-riscv-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1113.117~20.04.2 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 5.15.0-202.212 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 5.15.0-1119.126 - Upgrade
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ubuntu/linux-aws-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1032.34~22.04.1 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 5.15.0-1125.134 - Upgrade
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ubuntu/linux-azure-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1034.39~22.04.1 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 5.15.0-1124.133 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 5.15.0-1120.130 - Upgrade
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ubuntu/linux-gcp-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1033.35~22.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 5.15.0-1115.121 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 5.15.0-1102.110 - Upgrade
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ubuntu/linux-hwe-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-64.67~22.04.1 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 5.15.0-1113.117 - Upgrade
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ubuntu/linux-ibm-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1029.29~22.04.1 - Upgrade
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ubuntu/linux-intel-iotgto a version that resolves this vulnerability.Fixed in 5.15.0-1114.120 - Upgrade
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ubuntu/linux-kvmto a version that resolves this vulnerability.Fixed in 5.15.0-1111.116 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 5.15.0-197.207 - Upgrade
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ubuntu/linux-lowlatency-hwe-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-64.67.1~22.04.1 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 5.15.0-1114.115 - Upgrade
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ubuntu/linux-nvidia-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1031.34~22.04.1 - Upgrade
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ubuntu/linux-nvidia-tegrato a version that resolves this vulnerability.Fixed in 5.15.0-1070.72 - Upgrade
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ubuntu/linux-nvidia-tegra-igxto a version that resolves this vulnerability.Fixed in 5.15.0-1059.59 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 5.15.0-1116.122 - Upgrade
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ubuntu/linux-oracle-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1029.30~22.04.1 - Upgrade
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ubuntu/linux-riscv-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-64.67~22.04.1 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 5.15.0-1103.105 - Upgrade
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ubuntu/linux-intel-iot-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1111.115 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1118.127 - Upgrade
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ubuntu/linux-realtime-6.8to a version that resolves this vulnerability.Fixed in 6.8.1-1025.26~22.04.1 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1119.126+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1125.134+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-202.212+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1120.130+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-64.67 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1032.34 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1034.39 - Upgrade
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ubuntu/linux-azure-6.11to a version that resolves this vulnerability.Fixed in 6.11.0-1015.15~24.04.1 - Upgrade
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ubuntu/linux-azure-nvidiato a version that resolves this vulnerability.Fixed in 6.8.0-1022.23 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1033.35 - Upgrade
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ubuntu/linux-gcp-6.11to a version that resolves this vulnerability.Fixed in 6.11.0-1015.15~24.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1028.32 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 6.8.0-1015.17 - Upgrade
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ubuntu/linux-hwe-6.11to a version that resolves this vulnerability.Fixed in 6.11.0-26.26~24.04.1 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 6.8.0-1029.29 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-64.67.1 - Upgrade
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ubuntu/linux-lowlatency-hwe-6.11to a version that resolves this vulnerability.Fixed in 6.11.0-1014.15~24.04.1 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 6.8.0-1031.34 - Upgrade
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ubuntu/linux-nvidia-6.11to a version that resolves this vulnerability.Fixed in 6.11.0-1010.10 - Upgrade
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ubuntu/linux-nvidia-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-1031.34.1 - Upgrade
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ubuntu/linux-nvidia-tegrato a version that resolves this vulnerability.Fixed in 6.8.0-1008.8 - Upgrade
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ubuntu/linux-oem-6.11to a version that resolves this vulnerability.Fixed in 6.11.0-1022.22 - Upgrade
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ubuntu/linux-oem-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1031.31 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1029.30 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 6.8.0-1031.35 - Upgrade
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ubuntu/linux-xilinxto a version that resolves this vulnerability.Fixed in 6.8.0-1017.18 - Upgrade
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ubuntu/linux-raspi-realtimeto a version that resolves this vulnerability.Fixed in 6.8.0-2026.27 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1025.26 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-78.78+fips1 - Compensating control
In the AX.25 implementation, remove the RTNL dependency from ax25_setsockopt() and RCU-protect dev->ax25_ptr to address the lock dependency and potential use-after-free issues.
Event History
Frequently Asked Questions
Which Ubuntu kernel packages are identified as affected?
The affected software list includes ubuntu/linux, ubuntu/linux-aws, ubuntu/linux-azure, ubuntu/linux-gcp, ubuntu/linux-oracle, ubuntu/linux-fips, ubuntu/linux-aws-fips, and ubuntu/linux-azure-fips.
What level of access does an attacker need to exploit this issue?
The supplied CVSS vector indicates local access, low attack complexity, no user interaction, and high privileges required. This points to a risk primarily for attackers or processes that already have high local privileges.
What is the potential impact if exploited?
The supplied CVSS vector rates confidentiality, integrity, and availability impact as high, with no stated impact on a subsequent system. The vulnerability description also identifies possible use-after-free conditions in AX.25 handling.