Re: [syzbot] [net?] possible deadlock in gtp_encap_enable_socket

[Pablo Neira Ayuso <pablo@netfilter.org>]

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.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/ba253eabab42/vmlinux-94106455.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/569982fb6c88/bzImage-94106455.xz
> 
> 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
> ------------------------------------------------------
> 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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> 
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