Re: [syzbot] [net?] possible deadlock in rtnl_lock (8)

[Eric Dumazet]

On Sun, Sep 8, 2024 at 10:12 AM syzbot
<syzbot+51cf7cc5f9ffc1006ef2@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    df54f4a16f82 Merge branch 'for-next/core' into for-kernelci
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=12bdabc7980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=dde5a5ba8d41ee9e
> dashboard link: https://syzkaller.appspot.com/bug?extid=51cf7cc5f9ffc1006ef2
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1798589f980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10a30e00580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/aa2eb06e0aea/disk-df54f4a1.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/14728733d385/vmlinux-df54f4a1.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/99816271407d/Image-df54f4a1.gz.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+51cf7cc5f9ffc1006ef2@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.11.0-rc5-syzkaller-gdf54f4a16f82 #0 Not tainted
> ------------------------------------------------------
> syz-executor272/6388 is trying to acquire lock:
> ffff8000923b6ce8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:79
>
> but task is already holding lock:
> ffff0000dc408a50 (&smc->clcsock_release_lock){+.+.}-{3:3}, at: smc_setsockopt+0x178/0x10fc net/smc/af_smc.c:3064
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #2 (&smc->clcsock_release_lock){+.+.}-{3:3}:
>        __mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:608
>        __mutex_lock kernel/locking/mutex.c:752 [inline]
>        mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:804
>        smc_switch_to_fallback+0x48/0xa80 net/smc/af_smc.c:902
>        smc_sendmsg+0xfc/0x9f8 net/smc/af_smc.c:2779
>        sock_sendmsg_nosec net/socket.c:730 [inline]
>        __sock_sendmsg net/socket.c:745 [inline]
>        __sys_sendto+0x374/0x4f4 net/socket.c:2204
>        __do_sys_sendto net/socket.c:2216 [inline]
>        __se_sys_sendto net/socket.c:2212 [inline]
>        __arm64_sys_sendto+0xd8/0xf8 net/socket.c:2212
>        __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
>        invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
>        el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
>        do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
>        el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
>        el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
>        el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
>
> -> #1 (sk_lock-AF_INET){+.+.}-{0:0}:
>        lock_sock_nested net/core/sock.c:3543 [inline]
>        lock_sock include/net/sock.h:1607 [inline]
>        sockopt_lock_sock+0x88/0x148 net/core/sock.c:1061
>        do_ip_setsockopt+0x1438/0x346c net/ipv4/ip_sockglue.c:1078
>        ip_setsockopt+0x80/0x128 net/ipv4/ip_sockglue.c:1417
>        raw_setsockopt+0x100/0x294 net/ipv4/raw.c:845
>        sock_common_setsockopt+0xb0/0xcc net/core/sock.c:3735
>        do_sock_setsockopt+0x2a0/0x4e0 net/socket.c:2324
>        __sys_setsockopt+0x128/0x1a8 net/socket.c:2347
>        __do_sys_setsockopt net/socket.c:2356 [inline]
>        __se_sys_setsockopt net/socket.c:2353 [inline]
>        __arm64_sys_setsockopt+0xb8/0xd4 net/socket.c:2353
>        __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
>        invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
>        el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
>        do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
>        el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
>        el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
>        el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
>
> -> #0 (rtnl_mutex){+.+.}-{3:3}:
>        check_prev_add kernel/locking/lockdep.c:3133 [inline]
>        check_prevs_add kernel/locking/lockdep.c:3252 [inline]
>        validate_chain kernel/locking/lockdep.c:3868 [inline]
>        __lock_acquire+0x33d8/0x779c kernel/locking/lockdep.c:5142
>        lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759
>        __mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:608
>        __mutex_lock kernel/locking/mutex.c:752 [inline]
>        mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:804
>        rtnl_lock+0x20/0x2c net/core/rtnetlink.c:79
>        do_ip_setsockopt+0xe8c/0x346c net/ipv4/ip_sockglue.c:1077
>        ip_setsockopt+0x80/0x128 net/ipv4/ip_sockglue.c:1417
>        tcp_setsockopt+0xcc/0xe8 net/ipv4/tcp.c:3768
>        sock_common_setsockopt+0xb0/0xcc net/core/sock.c:3735
>        smc_setsockopt+0x204/0x10fc net/smc/af_smc.c:3072
>        do_sock_setsockopt+0x2a0/0x4e0 net/socket.c:2324
>        __sys_setsockopt+0x128/0x1a8 net/socket.c:2347
>        __do_sys_setsockopt net/socket.c:2356 [inline]
>        __se_sys_setsockopt net/socket.c:2353 [inline]
>        __arm64_sys_setsockopt+0xb8/0xd4 net/socket.c:2353
>        __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
>        invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
>        el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
>        do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
>        el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
>        el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
>        el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
>
> other info that might help us debug this:
>
> Chain exists of:
>   rtnl_mutex --> sk_lock-AF_INET --> &smc->clcsock_release_lock
>
>  Possible unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   lock(&smc->clcsock_release_lock);
>                                lock(sk_lock-AF_INET);
>                                lock(&smc->clcsock_release_lock);
>   lock(rtnl_mutex);
>
>  *** DEADLOCK ***
>
> 1 lock held by syz-executor272/6388:
>  #0: ffff0000dc408a50 (&smc->clcsock_release_lock){+.+.}-{3:3}, at: smc_setsockopt+0x178/0x10fc net/smc/af_smc.c:3064
>
> stack backtrace:
> CPU: 1 UID: 0 PID: 6388 Comm: syz-executor272 Not tainted 6.11.0-rc5-syzkaller-gdf54f4a16f82 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
> Call trace:
>  dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:317
>  show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324
>  __dump_stack lib/dump_stack.c:93 [inline]
>  dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:119
>  dump_stack+0x1c/0x28 lib/dump_stack.c:128
>  print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2059
>  check_noncircular+0x310/0x404 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 kernel/locking/lockdep.c:3868 [inline]
>  __lock_acquire+0x33d8/0x779c kernel/locking/lockdep.c:5142
>  lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759
>  __mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:608
>  __mutex_lock kernel/locking/mutex.c:752 [inline]
>  mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:804
>  rtnl_lock+0x20/0x2c net/core/rtnetlink.c:79
>  do_ip_setsockopt+0xe8c/0x346c net/ipv4/ip_sockglue.c:1077
>  ip_setsockopt+0x80/0x128 net/ipv4/ip_sockglue.c:1417
>  tcp_setsockopt+0xcc/0xe8 net/ipv4/tcp.c:3768
>  sock_common_setsockopt+0xb0/0xcc net/core/sock.c:3735
>  smc_setsockopt+0x204/0x10fc net/smc/af_smc.c:3072
>  do_sock_setsockopt+0x2a0/0x4e0 net/socket.c:2324
>  __sys_setsockopt+0x128/0x1a8 net/socket.c:2347
>  __do_sys_setsockopt net/socket.c:2356 [inline]
>  __se_sys_setsockopt net/socket.c:2353 [inline]
>  __arm64_sys_setsockopt+0xb8/0xd4 net/socket.c:2353
>  __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
>  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
>  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
>  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
>  el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
>  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
>  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
>
>
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.

Please SMC folks, can you take a look ?