Cc'ing SMC maintainers.

syzkaller combining layer is a crazy way to find crashes.

I think this is a false possible lockdep considers smc->clcsock_release_lock is a lock of the same class sk_lock-AF_INET.

this can be solved with lockdep_set_class in af_smc?

Thanks.

On Mon, Sep 23, 2024 at 08:46:24AM -0700, syzbot wrote:

Hello,

syzbot found the following issue on:

HEAD commit: 9410645520e9 Merge tag 'net-next-6.12' of git://git.kernel.. git tree: net-next console+strace: https://syzkaller.appspot.com/x/log.txt?x=15d39e9f980000 kernel config: https://syzkaller.appspot.com/x/.config?x=37c006d80708398d dashboard link: https://syzkaller.appspot.com/bug?extid=e953a8f3071f5c0a28fd compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16215ca9980000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=110c6c27980000

Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/80466d230dfb/disk-94106455.raw.... vmlinux: https://storage.googleapis.com/syzbot-assets/ba253eabab42/vmlinux-94106455.x... kernel image: https://storage.googleapis.com/syzbot-assets/569982fb6c88/bzImage-94106455.x...

IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+e953a8f3071f5c0a28fd@syzkaller.appspotmail.com

IPVS: Unknown mcast interface: macvlan0 netlink: 8 bytes leftover after parsing attributes in process `syz-executor297'. netlink: 24 bytes leftover after parsing attributes in process `syz-executor297'. ====================================================== WARNING: possible circular locking dependency detected 6.11.0-syzkaller-01458-g9410645520e9 #0 Not tainted

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syz-executor297/5243 is trying to acquire lock: ffff88801cf99158 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline] ffff88801cf99158 (sk_lock-AF_INET){+.+.}-{0:0}, at: gtp_encap_enable_socket+0x2ce/0x5c0 drivers/net/gtp.c:1674

but task is already holding lock: ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline] ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (rtnl_mutex){+.+.}-{3:3}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759 __mutex_lock_common kernel/locking/mutex.c:608 [inline] __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 start_sync_thread+0xdc/0x2dc0 net/netfilter/ipvs/ip_vs_sync.c:1761 do_ip_vs_set_ctl+0x442/0x13d0 net/netfilter/ipvs/ip_vs_ctl.c:2732 nf_setsockopt+0x295/0x2c0 net/netfilter/nf_sockopt.c:101 smc_setsockopt+0x275/0xe50 net/smc/af_smc.c:3064 do_sock_setsockopt+0x3af/0x720 net/socket.c:2330 __sys_setsockopt+0x1ae/0x250 net/socket.c:2353 __do_sys_setsockopt net/socket.c:2362 [inline] __se_sys_setsockopt net/socket.c:2359 [inline] __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2359 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&smc->clcsock_release_lock){+.+.}-{3:3}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759 __mutex_lock_common kernel/locking/mutex.c:608 [inline] __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 smc_switch_to_fallback+0x35/0xdb0 net/smc/af_smc.c:902 smc_sendmsg+0x11f/0x530 net/smc/af_smc.c:2771 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:745 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2603 ___sys_sendmsg net/socket.c:2657 [inline] __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2686 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sk_lock-AF_INET){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3133 [inline] check_prevs_add kernel/locking/lockdep.c:3252 [inline] validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868 __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759 lock_sock_nested+0x48/0x100 net/core/sock.c:3611 lock_sock include/net/sock.h:1609 [inline] gtp_encap_enable_socket+0x2ce/0x5c0 drivers/net/gtp.c:1674 gtp_encap_enable drivers/net/gtp.c:1707 [inline] gtp_newlink+0x589/0xf30 drivers/net/gtp.c:1511 rtnl_newlink_create net/core/rtnetlink.c:3510 [inline] __rtnl_newlink net/core/rtnetlink.c:3730 [inline] rtnl_newlink+0x1591/0x20a0 net/core/rtnetlink.c:3743 rtnetlink_rcv_msg+0x73f/0xcf0 net/core/rtnetlink.c:6646 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline] netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357 netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:745 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2603 ___sys_sendmsg net/socket.c:2657 [inline] __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2686 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 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 ***

1 lock held by syz-executor297/5243: #0: ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline] #0: ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643

stack backtrace: CPU: 0 UID: 0 PID: 5243 Comm: syz-executor297 Not tainted 6.11.0-syzkaller-01458-g9410645520e9 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 Call Trace:

<TASK> __dump_stack lib/dump_stack.c:93 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2186 check_prev_add kernel/locking/lockdep.c:3133 [inline] check_prevs_add kernel/locking/lockdep.c:3252 [inline] validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868 __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759 lock_sock_nested+0x48/0x100 net/core/sock.c:3611 lock_sock include/net/sock.h:1609 [inline] gtp_encap_enable_socket+0x2ce/0x5c0 drivers/net/gtp.c:1674 gtp_encap_enable drivers/net/gtp.c:1707 [inline] gtp_newlink+0x589/0xf30 drivers/net/gtp.c:1511 rtnl_newlink_create net/core/rtnetlink.c:3510 [inline] __rtnl_newlink net/core/rtnetlink.c:3730 [inline] rtnl_newlink+0x1591/0x20a0 net/core/rtnetlink.c:3743 rtnetlink_rcv_msg+0x73f/0xcf0 net/core/rtnetlink.c:6646 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline] netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357 netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:745 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2603 ___sys_sendmsg net/socket.c:2657 [inline] __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2686 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fed198844a9 Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 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 b8 ff ff ff f7 d8 64 89 01 48 RS

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