Re: [syzbot] [net?] possible deadlock in ipv6_sock_ac_close (4)

[syzbot <syzbot+be6f4b383534d88989f7@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    e48e99b6edf4 Merge tag 'pull-fixes' of git://git.kernel.or..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=12afa7cf980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f2054704dd53fb80
dashboard link: https://syzkaller.appspot.com/bug?extid=be6f4b383534d88989f7
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=140a294c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1486994c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b03407c4ab24/disk-e48e99b6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/03f6746c0414/vmlinux-e48e99b6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4b3909ad8728/bzImage-e48e99b6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+be6f4b383534d88989f7@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.14.0-syzkaller-13189-ge48e99b6edf4 #0 Not tainted
------------------------------------------------------
syz-executor200/5838 is trying to acquire lock:
ffffffff900fc808 (rtnl_mutex){+.+.}-{4:4}, at: ipv6_sock_ac_close+0xc9/0x130 net/ipv6/anycast.c:220

but task is already holding lock:
ffff888035260aa0 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_clcsock_release+0x82/0xf0 net/smc/smc_close.c:30

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&smc->clcsock_release_lock){+.+.}-{4:4}:
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
       smc_switch_to_fallback+0x35/0xda0 net/smc/af_smc.c:903
       smc_setsockopt+0x765/0xd50 net/smc/af_smc.c:3104
       do_sock_setsockopt+0x3b1/0x710 net/socket.c:2296
       __sys_setsockopt net/socket.c:2321 [inline]
       __do_sys_setsockopt net/socket.c:2327 [inline]
       __se_sys_setsockopt net/socket.c:2324 [inline]
       __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2324
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       lock_sock_nested+0x48/0x100 net/core/sock.c:3697
       do_ipv6_setsockopt+0xccd/0x3680 net/ipv6/ipv6_sockglue.c:567
       ipv6_setsockopt+0x5d/0x170 net/ipv6/ipv6_sockglue.c:993
       do_sock_setsockopt+0x3b1/0x710 net/socket.c:2296
       __sys_setsockopt net/socket.c:2321 [inline]
       __do_sys_setsockopt net/socket.c:2327 [inline]
       __se_sys_setsockopt net/socket.c:2324 [inline]
       __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2324
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (rtnl_mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain+0xa69/0x24e0 kernel/locking/lockdep.c:3909
       __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
       ipv6_sock_ac_close+0xc9/0x130 net/ipv6/anycast.c:220
       inet6_release+0x4f/0x70 net/ipv6/af_inet6.c:485
       __sock_release net/socket.c:647 [inline]
       sock_release+0x82/0x150 net/socket.c:675
       smc_clcsock_release+0xcc/0xf0 net/smc/smc_close.c:34
       __smc_release+0x683/0x800 net/smc/af_smc.c:301
       smc_release+0x2dc/0x540 net/smc/af_smc.c:344
       __sock_release net/socket.c:647 [inline]
       sock_close+0xbc/0x240 net/socket.c:1391
       __fput+0x3e9/0x9f0 fs/file_table.c:465
       task_work_run+0x251/0x310 kernel/task_work.c:227
       exit_task_work include/linux/task_work.h:40 [inline]
       do_exit+0xa11/0x27f0 kernel/exit.c:953
       do_group_exit+0x207/0x2c0 kernel/exit.c:1102
       __do_sys_exit_group kernel/exit.c:1113 [inline]
       __se_sys_exit_group kernel/exit.c:1111 [inline]
       __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1111
       x64_sys_call+0x26c3/0x26d0 arch/x86/include/generated/asm/syscalls_64.h:232
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf3/0x230 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:
  rtnl_mutex --> sk_lock-AF_INET6 --> &smc->clcsock_release_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&smc->clcsock_release_lock);
                               lock(sk_lock-AF_INET6);
                               lock(&smc->clcsock_release_lock);
  lock(rtnl_mutex);

 *** DEADLOCK ***

2 locks held by syz-executor200/5838:
 #0: ffff888078efc408 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:867 [inline]
 #0: ffff888078efc408 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: __sock_release net/socket.c:646 [inline]
 #0: ffff888078efc408 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: sock_close+0x90/0x240 net/socket.c:1391
 #1: ffff888035260aa0 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_clcsock_release+0x82/0xf0 net/smc/smc_close.c:30

stack backtrace:
CPU: 0 UID: 0 PID: 5838 Comm: syz-executor200 Not tainted 6.14.0-syzkaller-13189-ge48e99b6edf4 #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+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2079
 check_noncircular+0x142/0x160 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+0xa69/0x24e0 kernel/locking/lockdep.c:3909
 __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235
 lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
 __mutex_lock_common kernel/locking/mutex.c:601 [inline]
 __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
 ipv6_sock_ac_close+0xc9/0x130 net/ipv6/anycast.c:220
 inet6_release+0x4f/0x70 net/ipv6/af_inet6.c:485
 __sock_release net/socket.c:647 [inline]
 sock_release+0x82/0x150 net/socket.c:675
 smc_clcsock_release+0xcc/0xf0 net/smc/smc_close.c:34
 __smc_release+0x683/0x800 net/smc/af_smc.c:301
 smc_release+0x2dc/0x540 net/smc/af_smc.c:344
 __sock_release net/socket.c:647 [inline]
 sock_close+0xbc/0x240 net/socket.c:1391
 __fput+0x3e9/0x9f0 fs/file_table.c:465
 task_work_run+0x251/0x310 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0xa11/0x27f0 kernel/exit.c:953
 do_group_exit+0x207/0x2c0 kernel/exit.c:1102
 __do_sys_exit_group kernel/exit.c:1113 [inline]
 __se_sys_exit_group kernel/exit.c:1111 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1111
 x64_sys_call+0x26c3/0x26d0 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd6e1b18d39
Code: Unable to access opcode bytes at 0x7fd6e1b18d0f.
R


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