netrom: fix possible dead-lock in nr_rt_ioctl()

Summary

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---

Timeline

1. Jun 19, 2024, 1:45 PM UTCCVE published
2. Sep 10, 2024, 5:13 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Oct 15, 2026, 12:43 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in b9d663fbf74290cb68fbc66ae4367bd56837ad1d; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 1fbfb483c1a290dce3f41f52d45cc46dd88b7691; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in b117e5b4f27c2c9076561b6be450a9619f0b79de; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 421c50fa81836775bf0fd6ce0e57a6eb27af24d5; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 3db2fc45d1d2a6457f06ebdfd45b9820e5b5c2b7; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in f28bdc2ee5d9300cc77bd3d97b5b3cdd14960fd8; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 5fb7e2a4335fc67d6952ad2a6613c46e0b05f7c5; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 5bc50a705cfac8f64ce51c95611c3dd0554ef9c3; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in e03e7f20ebf7e1611d40d1fdc1bde900fd3335f6

• Linux Linux

  2.6.12

• KernelLinux

  From 2.6.12 · fixed in 4.19.316; From 4.20.0 · fixed in 5.4.278; From 5.5.0 · fixed in 5.10.219; From 5.11.0 · fixed in 5.15.161; From 5.16.0 · fixed in 6.1.93; From 6.2.0 · fixed in 6.6.33; From 6.7.0 · fixed in 6.8.12; From 6.9.0 · fixed in 6.9.3

References 9