Re: [syzbot] [net?] [s390?] possible deadlock in smc_switch_to_fallback (2)

[syzbot <syzbot+bef85a6996d1737c1a2f@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    1722389b0d86 Merge tag 'net-6.11-rc1' of git://git.kernel...
git tree:       net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10affabd980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5efb917b1462a973
dashboard link: https://syzkaller.appspot.com/bug?extid=bef85a6996d1737c1a2f
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=14d70365980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17565655980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f6e80669686a/disk-1722389b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ee658b141f49/vmlinux-1722389b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/35cfa877b1af/bzImage-1722389b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bef85a6996d1737c1a2f@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.10.0-syzkaller-12562-g1722389b0d86 #0 Not tainted
------------------------------------------------------
syz-executor383/5226 is trying to acquire lock:
ffff888022c58a50 (&smc->clcsock_release_lock){+.+.}-{3:3}, at: smc_switch_to_fallback+0x35/0xd00 net/smc/af_smc.c:902

but task is already holding lock:
ffff888022c58258 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1607 [inline]
ffff888022c58258 (sk_lock-AF_INET){+.+.}-{0:0}, at: smc_sendmsg+0x55/0x530 net/smc/af_smc.c:2773

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
       lock_sock_nested+0x48/0x100 net/core/sock.c:3543
       do_ip_setsockopt+0x1a2d/0x3cd0 net/ipv4/ip_sockglue.c:1078
       ip_setsockopt+0x63/0x100 net/ipv4/ip_sockglue.c:1417
       do_sock_setsockopt+0x3af/0x720 net/socket.c:2324
       __sys_setsockopt+0x1ae/0x250 net/socket.c:2347
       __do_sys_setsockopt net/socket.c:2356 [inline]
       __se_sys_setsockopt net/socket.c:2353 [inline]
       __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2353
       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 (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:3072
       do_sock_setsockopt+0x3af/0x720 net/socket.c:2324
       __sys_setsockopt+0x1ae/0x250 net/socket.c:2347
       __do_sys_setsockopt net/socket.c:2356 [inline]
       __se_sys_setsockopt net/socket.c:2353 [inline]
       __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2353
       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 (&smc->clcsock_release_lock){+.+.}-{3:3}:
       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
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       smc_switch_to_fallback+0x35/0xd00 net/smc/af_smc.c:902
       smc_sendmsg+0x11f/0x530 net/smc/af_smc.c:2779
       sock_sendmsg_nosec net/socket.c:730 [inline]
       __sock_sendmsg+0x221/0x270 net/socket.c:745
       __sys_sendto+0x3a4/0x4f0 net/socket.c:2204
       __do_sys_sendto net/socket.c:2216 [inline]
       __se_sys_sendto net/socket.c:2212 [inline]
       __x64_sys_sendto+0xde/0x100 net/socket.c:2212
       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:
  &smc->clcsock_release_lock --> rtnl_mutex --> sk_lock-AF_INET

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz-executor383/5226:
 #0: ffff888022c58258 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1607 [inline]
 #0: ffff888022c58258 (sk_lock-AF_INET){+.+.}-{0:0}, at: smc_sendmsg+0x55/0x530 net/smc/af_smc.c:2773

stack backtrace:
CPU: 1 UID: 0 PID: 5226 Comm: syz-executor383 Not tainted 6.10.0-syzkaller-12562-g1722389b0d86 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
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
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 smc_switch_to_fallback+0x35/0xd00 net/smc/af_smc.c:902
 smc_sendmsg+0x11f/0x530 net/smc/af_smc.c:2779
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 __sys_sendto+0x3a4/0x4f0 net/socket.c:2204
 __do_sys_sendto net/socket.c:2216 [inline]
 __se_sys_sendto net/socket.c:2212 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2212
 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: 0033:0x7f1c3ca27ab9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 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
RSP: 002b:00007fffe06c23b8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1c3ca27ab9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007f1c3ca9a5f0 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000200007fd R11: 0000000000000246 R12: 0000000000000001
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
 </TASK>


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