CVE-2025-40280: tipc: Fix use-after-free in tipc_mon_reinit_self().

In the Linux kernel, the following vulnerability has been resolved:

tipc: Fix use-after-free in tipcmonreinitself().

syzbot reported use-after-free of tipcnet(net)->monitors[] in tipcmonreinitself(). [0]

The array is protected by RTNL, but tipcmonreinitself() iterates over it without RTNL.

tipcmonreinitself() is called from tipcnetfinalize(), which is always under RTNL except for tipcnetfinalizework().

Let's hold RTNL in tipcnetfinalizework().

[0]: BUG: KASAN: slab-use-after-free in rawspinlockirqsave include/linux/spinlockapismp.h:110 [inline] BUG: KASAN: slab-use-after-free in rawspinlockirqsave+0xa7/0xf0 kernel/locking/spinlock.c:162 Read of size 1 at addr ffff88805eae1030 by task kworker/0:7/5989

CPU: 0 UID: 0 PID: 5989 Comm: kworker/0:7 Not tainted syzkaller #0 PREEMPT{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025 Workqueue: events tipcnetfinalizework Call Trace: <TASK> dumpstacklvl+0x189/0x250 lib/dumpstack.c:120 printaddressdescription mm/kasan/report.c:378 [inline] printreport+0xca/0x240 mm/kasan/report.c:482 kasanreport+0x118/0x150 mm/kasan/report.c:595 kasancheckbyte+0x2a/0x40 mm/kasan/common.c:568 kasancheckbyte include/linux/kasan.h:399 [inline] lockacquire+0x8d/0x360 kernel/locking/lockdep.c:5842 rawspinlockirqsave include/linux/spinlockapismp.h:110 [inline] rawspinlockirqsave+0xa7/0xf0 kernel/locking/spinlock.c:162 rtlockslowlock kernel/locking/rtmutex.c:1894 [inline] rwbasertmutexlockstate kernel/locking/spinlockrt.c:160 [inline] rwbasewritelock+0xd3/0x7e0 kernel/locking/rwbasert.c:244 rtwritelock+0x76/0x110 kernel/locking/spinlockrt.c:243 writelockbh include/linux/rwlockrt.h:99 [inline] tipcmonreinitself+0x79/0x430 net/tipc/monitor.c:718 tipcnetfinalize+0x115/0x190 net/tipc/net.c:140 processonework kernel/workqueue.c:3236 [inline] processscheduledworks+0xade/0x17b0 kernel/workqueue.c:3319 workerthread+0x8a0/0xda0 kernel/workqueue.c:3400 kthread+0x70e/0x8a0 kernel/kthread.c:463 retfromfork+0x439/0x7d0 arch/x86/kernel/process.c:148 retfromforkasm+0x1a/0x30 arch/x86/entry/entry64.S:245 </TASK>

Allocated by task 6089: kasansavestack mm/kasan/common.c:47 [inline] kasansavetrack+0x3e/0x80 mm/kasan/common.c:68 poisonkmallocredzone mm/kasan/common.c:388 [inline] kasankmalloc+0x93/0xb0 mm/kasan/common.c:405 kasankmalloc include/linux/kasan.h:260 [inline] kmalloccachenoprof+0x1a8/0x320 mm/slub.c:4407 kmallocnoprof include/linux/slab.h:905 [inline] kzallocnoprof include/linux/slab.h:1039 [inline] tipcmoncreate+0xc3/0x4d0 net/tipc/monitor.c:657 tipcenablebearer net/tipc/bearer.c:357 [inline] tipcnlbearerenable+0xe16/0x13f0 net/tipc/bearer.c:1047 tipcnlcompatdoit net/tipc/netlinkcompat.c:371 [inline] tipcnlcompatdoit+0x3bc/0x5f0 net/tipc/netlinkcompat.c:393 tipcnlcompathandle net/tipc/netlinkcompat.c:-1 [inline] tipcnlcompatrecv+0x83c/0xbe0 net/tipc/netlinkcompat.c:1321 genlfamilyrcvmsgdoit+0x215/0x300 net/netlink/genetlink.c:1115 genlfamilyrcvmsg net/netlink/genetlink.c:1195 [inline] genlrcvmsg+0x60e/0x790 net/netlink/genetlink.c:1210 netlinkrcvskb+0x208/0x470 net/netlink/afnetlink.c:2552 genlrcv+0x28/0x40 net/netlink/genetlink.c:1219 netlinkunicastkernel net/netlink/afnetlink.c:1320 [inline] netlinkunicast+0x846/0xa10 net/netlink/afnetlink.c:1346 netlinksendmsg+0x805/0xb30 net/netlink/afnetlink.c:1896 socksendmsgnosec net/socket.c:714 [inline] socksendmsg+0x21c/0x270 net/socket.c:729 syssendmsg+0x508/0x820 net/socket.c:2614 syssendmsg+0x21f/0x2a0 net/socket.c:2668 syssendmsg net/socket.c:2700 [inline] dosyssendmsg net/socket.c:2705 [inline] sesyssendmsg net/socket.c:2703 [inline] x64syssendmsg+0x1a1/0x260 net/socket.c:2703 dosyscallx64 arch/x86/entry/syscall64.c:63 [inline] dosyscall64+0xfa/0x3b0 arch/ ---truncated---