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

[syzbot <syzbot+51cf7cc5f9ffc1006ef2@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in rtnl_lock

======================================================
WARNING: possible circular locking dependency detected
6.11.0-rc7-syzkaller-g7e3e2c7f05cd-dirty #0 Not tainted
------------------------------------------------------
syz.0.15/7317 is trying to acquire lock:
ffff8000923b7ea8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:79

but task is already holding lock:
ffff0000d4798a58 (&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.0.15/7317:
 #0: ffff0000d4798a58 (&smc->clcsock_release_lock){+.+.}-{3:3}, at: smc_setsockopt+0x178/0x10fc net/smc/af_smc.c:3064

stack backtrace:
CPU: 1 UID: 0 PID: 7317 Comm: syz.0.15 Not tainted 6.11.0-rc7-syzkaller-g7e3e2c7f05cd-dirty #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:319
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:326
 __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


Tested on:

commit:         7e3e2c7f 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=13b56100580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=921accd5d8340211
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16856100580000