CVE-2024-38589: In the Linux kernel, the following vulnerability has been resolved:  netrom: fix possible dead-lock in nr_rt_ioctl()  syzbot loves netrom, and found a possible deadlock in nr_rt_ioctl [1]  Make sure we always acquire nr_node_list_lock before nr_node_lock(nr_node)  [1] WARNING: possible circular locking dependency detected 6.9.0-rc7-syzkaller-02147-g654de42f3fc6 #0 Not tainted ------------------------------------------------------ syz-executor350/5129 is trying to acquire lock:  ffff8880186e2070 (&nr_node->node_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]  ffff8880186e2070 (&nr_node->node_lock){+...}-{2:2}, at: nr_node_lock include/net/netrom.h:152 [inline]  ffff8880186e2070 (&nr_node->node_lock){+...}-{2:2}, at: nr_dec_obs net/netrom/nr_route.c:464 [inline]  ffff8880186e2070 (&nr_node->node_lock){+...}-{2:2}, at: nr_rt_ioctl+0x1bb/0x1090 net/netrom/nr_route.c:697  but task is already holding lock:  ffffffff8f7053b8 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]  ffffffff8f7053b8 (nr_node_list_lock){+...}-{2:2}, at: nr_dec_obs net/netrom/nr_route.c:462 [inline]  ffffffff8f7053b8 (nr_node_list_lock){+...}-{2:2}, at: nr_rt_ioctl+0x10a/0x1090 net/netrom/nr_route.c:697  which lock already depends on the new lock.  the existing dependency chain (in reverse order) is:  -> #1 (nr_node_list_lock){+...}-{2:2}:         lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754         __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]         _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178         spin_lock_bh include/linux/spinlock.h:356 [inline]         nr_remove_node net/netrom/nr_route.c:299 [inline]         nr_del_node+0x4b4/0x820 net/netrom/nr_route.c:355         nr_rt_ioctl+0xa95/0x1090 net/netrom/nr_route.c:683         sock_do_ioctl+0x158/0x460 net/socket.c:1222         sock_ioctl+0x629/0x8e0 net/socket.c:1341         vfs_ioctl fs/ioctl.c:51 [inline]         __do_sys_ioctl fs/ioctl.c:904 [inline]         __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:890         do_syscall_x64 arch/x86/entry/common.c:52 [inline]         do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83        entry_SYSCALL_64_after_hwframe+0x77/0x7f  -> #0 (&nr_node->node_lock){+...}-{2:2}:         check_prev_add kernel/locking/lockdep.c:3134 [inline]         check_prevs_add kernel/locking/lockdep.c:3253 [inline]         validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869         __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137         lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754         __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]         _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178         spin_lock_bh include/linux/spinlock.h:356 [inline]         nr_node_lock include/net/netrom.h:152 [inline]         nr_dec_obs net/netrom/nr_route.c:464 [inline]         nr_rt_ioctl+0x1bb/0x1090 net/netrom/nr_route.c:697         sock_do_ioctl+0x158/0x460 net/socket.c:1222         sock_ioctl+0x629/0x8e0 net/socket.c:1341         vfs_ioctl fs/ioctl.c:51 [inline]         __do_sys_ioctl fs/ioctl.c:904 [inline]         __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:890         do_syscall_x64 arch/x86/entry/common.c:52 [inline]         do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83        entry_SYSCALL_64_after_hwframe+0x77/0x7f  other info that might help us debug this:   Possible unsafe locking scenario:         CPU0                    CPU1        ----                    ----   lock(nr_node_list_lock);                                lock(&nr_node->node_lock);                                lock(nr_node_list_lock);   lock(&nr_node->node_lock);   *** DEADLOCK ***  1 lock held by syz-executor350/5129:   #0: ffffffff8f7053b8 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]   #0: ffffffff8f7053b8 (nr_node_list_lock){+...}-{2:2}, at: nr_dec_obs net/netrom/nr_route.c:462 [inline]   #0: ffffffff8f70 ---truncated---