{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-21812",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2025-21812"
  ],
  "published": "2025-02-27T20:00:18Z",
  "summary": "ax25: rcu protect dev->ax25_ptr",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nax25: rcu protect dev->ax25_ptr\n\nsyzbot found a lockdep issue [1].\n\nWe should remove ax25 RTNL dependency in ax25_setsockopt()\n\nThis should also fix a variety of possible UAF in ax25.\n\n[1]\n\nWARNING: possible circular locking dependency detected\n6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Not tainted\n------------------------------------------------------\nsyz.5.1818/12806 is trying to acquire lock:\n ffffffff8fcb3988 (rtnl_mutex){+.+.}-{4:4}, at: ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680\n\nbut task is already holding lock:\n ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]\n ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574\n\nwhich lock already depends on the new lock.\n\nthe existing dependency chain (in reverse order) is:\n\n-> #1 (sk_lock-AF_AX25){+.+.}-{0:0}:\n        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n        lock_sock_nested+0x48/0x100 net/core/sock.c:3642\n        lock_sock include/net/sock.h:1618 [inline]\n        ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]\n        ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146\n        notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85\n       __dev_notify_flags+0x207/0x400\n        dev_change_flags+0xf0/0x1a0 net/core/dev.c:9026\n        dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:563\n        dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:820\n        sock_do_ioctl+0x240/0x460 net/socket.c:1234\n        sock_ioctl+0x626/0x8e0 net/socket.c:1339\n        vfs_ioctl fs/ioctl.c:51 [inline]\n        __do_sys_ioctl fs/ioctl.c:906 [inline]\n        __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892\n        do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n       entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\n-> #0 (rtnl_mutex){+.+.}-{4:4}:\n        check_prev_add kernel/locking/lockdep.c:3161 [inline]\n        check_prevs_add kernel/locking/lockdep.c:3280 [inline]\n        validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904\n        __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226\n        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n        __mutex_lock_common kernel/locking/mutex.c:585 [inline]\n        __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735\n        ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680\n        do_sock_setsockopt+0x3af/0x720 net/socket.c:2324\n        __sys_setsockopt net/socket.c:2349 [inline]\n        __do_sys_setsockopt net/socket.c:2355 [inline]\n        __se_sys_setsockopt net/socket.c:2352 [inline]\n        __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2352\n        do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n       entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nother info that might help us debug this:\n\n Possible unsafe locking scenario:\n\n       CPU0                    CPU1\n       ----                    ----\n  lock(sk_lock-AF_AX25);\n                               lock(rtnl_mutex);\n                               lock(sk_lock-AF_AX25);\n  lock(rtnl_mutex);\n\n *** DEADLOCK ***\n\n1 lock held by syz.5.1818/12806:\n  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]\n  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574\n\nstack backtrace:\nCPU: 1 UID: 0 PID: 12806 Comm: syz.5.1818 Not tainted 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024\nCall Trace:\n <TASK>\n  __dump_stack lib/dump_stack.c:94 [inline]\n  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\n  print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074\n  check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206\n  check_prev_add kernel/locking/lockdep.c:3161 [inline]\n  check_prevs_add kernel/lockin\n---truncated---",
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    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-21812"
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      "url": "https://git.kernel.org/stable/c/2802ed4ced27ebd474828fc67ffd7d66f11e3605"
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      "url": "https://git.kernel.org/stable/c/95fc45d1dea8e1253f8ec58abc5befb71553d666"
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  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z"
  }
}