syzbot

netlink: 24 bytes leftover after parsing attributes in process `syz.2.539'.
======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc1-syzkaller-00301-g3bde70a2c827 #0 Not tainted
------------------------------------------------------
syz.2.539/8251 is trying to acquire lock:
ffff888079aae718 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1651 [inline]
ffff888079aae718 (sk_lock-AF_INET){+.+.}-{0:0}, at: gtp_encap_enable_socket+0x287/0x4f0 drivers/net/gtp.c:1676

but task is already holding lock:
ffffffff9012be68 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
ffffffff9012be68 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
ffffffff9012be68 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x600/0x2000 net/core/rtnetlink.c:4067

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (rtnl_mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
       start_sync_thread+0x120/0x28b0 net/netfilter/ipvs/ip_vs_sync.c:1761
       do_ip_vs_set_ctl+0x451/0x11d0 net/netfilter/ipvs/ip_vs_ctl.c:2732
       nf_setsockopt+0x8a/0xf0 net/netfilter/nf_sockopt.c:101
       ip_setsockopt+0xcb/0xf0 net/ipv4/ip_sockglue.c:1424
       tcp_setsockopt+0xa4/0x100 net/ipv4/tcp.c:4077
       smc_setsockopt+0x1b3/0xa00 net/smc/af_smc.c:3081
       do_sock_setsockopt+0x221/0x470 net/socket.c:2296
       __sys_setsockopt+0x1a0/0x230 net/socket.c:2321
       __do_sys_setsockopt net/socket.c:2327 [inline]
       __se_sys_setsockopt net/socket.c:2324 [inline]
       __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2324
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&smc->clcsock_release_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
       smc_switch_to_fallback+0x2d/0x9f0 net/smc/af_smc.c:903
       smc_sendmsg+0x13d/0x520 net/smc/af_smc.c:2781
       sock_sendmsg_nosec net/socket.c:712 [inline]
       __sock_sendmsg net/socket.c:727 [inline]
       __sys_sendto+0x495/0x510 net/socket.c:2180
       __do_sys_sendto net/socket.c:2187 [inline]
       __se_sys_sendto net/socket.c:2183 [inline]
       __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2183
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sk_lock-AF_INET){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain kernel/locking/lockdep.c:3909 [inline]
       __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235
       lock_acquire kernel/locking/lockdep.c:5866 [inline]
       lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
       lock_sock_nested+0x41/0xf0 net/core/sock.c:3702
       lock_sock include/net/sock.h:1651 [inline]
       gtp_encap_enable_socket+0x287/0x4f0 drivers/net/gtp.c:1676
       gtp_encap_enable drivers/net/gtp.c:1720 [inline]
       gtp_newlink+0xf93/0x1390 drivers/net/gtp.c:1513
       rtnl_newlink_create net/core/rtnetlink.c:3836 [inline]
       __rtnl_newlink net/core/rtnetlink.c:3953 [inline]
       rtnl_newlink+0xc42/0x2000 net/core/rtnetlink.c:4068
       rtnetlink_rcv_msg+0x95b/0xe90 net/core/rtnetlink.c:6958
       netlink_rcv_skb+0x16a/0x440 net/netlink/af_netlink.c:2534
       netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
       netlink_unicast+0x53a/0x7f0 net/netlink/af_netlink.c:1339
       netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883
       sock_sendmsg_nosec net/socket.c:712 [inline]
       __sock_sendmsg net/socket.c:727 [inline]
       ____sys_sendmsg+0xa95/0xc70 net/socket.c:2566
       ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620
       __sys_sendmsg+0x16d/0x220 net/socket.c:2652
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  sk_lock-AF_INET --> &smc->clcsock_release_lock --> rtnl_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(rtnl_mutex);
                               lock(&smc->clcsock_release_lock);
                               lock(rtnl_mutex);
  lock(sk_lock-AF_INET);

 *** DEADLOCK ***

2 locks held by syz.2.539/8251:
 #0: ffffffff908698a0 (&ops->srcu#2){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:161 [inline]
 #0: ffffffff908698a0 (&ops->srcu#2){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:253 [inline]
 #0: ffffffff908698a0 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x113/0x2c0 net/core/rtnetlink.c:574
 #1: ffffffff9012be68 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff9012be68 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #1: ffffffff9012be68 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x600/0x2000 net/core/rtnetlink.c:4067

stack backtrace:
CPU: 1 UID: 0 PID: 8251 Comm: syz.2.539 Not tainted 6.15.0-rc1-syzkaller-00301-g3bde70a2c827 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2079
 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2211
 check_prev_add kernel/locking/lockdep.c:3166 [inline]
 check_prevs_add kernel/locking/lockdep.c:3285 [inline]
 validate_chain kernel/locking/lockdep.c:3909 [inline]
 __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235
 lock_acquire kernel/locking/lockdep.c:5866 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
 lock_sock_nested+0x41/0xf0 net/core/sock.c:3702
 lock_sock include/net/sock.h:1651 [inline]
 gtp_encap_enable_socket+0x287/0x4f0 drivers/net/gtp.c:1676
 gtp_encap_enable drivers/net/gtp.c:1720 [inline]
 gtp_newlink+0xf93/0x1390 drivers/net/gtp.c:1513
 rtnl_newlink_create net/core/rtnetlink.c:3836 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3953 [inline]
 rtnl_newlink+0xc42/0x2000 net/core/rtnetlink.c:4068
 rtnetlink_rcv_msg+0x95b/0xe90 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x16a/0x440 net/netlink/af_netlink.c:2534
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x53a/0x7f0 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg net/socket.c:727 [inline]
 ____sys_sendmsg+0xa95/0xc70 net/socket.c:2566
 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620
 __sys_sendmsg+0x16d/0x220 net/socket.c:2652
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc6a358d169
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc6a4359038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fc6a37a6160 RCX: 00007fc6a358d169
RDX: 0000000000000000 RSI: 0000200000000040 RDI: 0000000000000004
RBP: 00007fc6a360e990 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fc6a37a6160 R15: 00007ffd5b712c38
 </TASK>