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

From: syzbot
Date: Wed Oct 09 2024 - 08:54:09 EST

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syzbot has found a reproducer for the following issue on:

HEAD commit: 75b607fab38d Merge tag 'sched_ext-for-6.12-rc2-fixes' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13fbd7d0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=667b897270c8ae6
dashboard link: https://syzkaller.appspot.com/bug?extid=819a360379cf16b5f0d3
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=176c0f07980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14af1327980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a7759a7b0126/disk-75b607fa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/734e9758ae9d/vmlinux-75b607fa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e23bee69aa18/bzImage-75b607fa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+819a360379cf16b5f0d3@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc2-syzkaller-00058-g75b607fab38d #0 Not tainted
------------------------------------------------------
syz-executor308/20073 is trying to acquire lock:
ffff88807c488a98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline]
ffff88807c488a98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: sockopt_lock_sock net/core/sock.c:1125 [inline]
ffff88807c488a98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: sockopt_lock_sock+0x54/0x70 net/core/sock.c:1116

but task is already holding lock:
ffffffff8fac31e8 (rtnl_mutex){+.+.}-{3:3}, at: do_ipv6_setsockopt+0x1f4d/0x4800 net/ipv6/ipv6_sockglue.c:566

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (rtnl_mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
do_ipv6_setsockopt+0x1f4d/0x4800 net/ipv6/ipv6_sockglue.c:566
ipv6_setsockopt+0xcb/0x170 net/ipv6/ipv6_sockglue.c:993
tcp_setsockopt+0xa4/0x100 net/ipv4/tcp.c:4029
smc_setsockopt+0x1b4/0xc00 net/smc/af_smc.c:3064
do_sock_setsockopt+0x222/0x480 net/socket.c:2329
__sys_setsockopt+0x1a4/0x270 net/socket.c:2352
__do_sys_setsockopt net/socket.c:2361 [inline]
__se_sys_setsockopt net/socket.c:2358 [inline]
__x64_sys_setsockopt+0xbd/0x160 net/socket.c:2358
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&smc->clcsock_release_lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
smc_switch_to_fallback+0x2d/0xa00 net/smc/af_smc.c:902
smc_setsockopt+0xa7b/0xc00 net/smc/af_smc.c:3087
do_sock_setsockopt+0x222/0x480 net/socket.c:2329
__sys_setsockopt+0x1a4/0x270 net/socket.c:2352
__do_sys_setsockopt net/socket.c:2361 [inline]
__se_sys_setsockopt net/socket.c:2358 [inline]
__x64_sys_setsockopt+0xbd/0x160 net/socket.c:2358
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sk_lock-AF_INET6){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain kernel/locking/lockdep.c:3904 [inline]
__lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5202
lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
lock_sock_nested+0x3a/0xf0 net/core/sock.c:3611
lock_sock include/net/sock.h:1609 [inline]
sockopt_lock_sock net/core/sock.c:1125 [inline]
sockopt_lock_sock+0x54/0x70 net/core/sock.c:1116
do_ipv6_setsockopt+0x1f55/0x4800 net/ipv6/ipv6_sockglue.c:567
ipv6_setsockopt+0xcb/0x170 net/ipv6/ipv6_sockglue.c:993
udpv6_setsockopt+0x7d/0xd0 net/ipv6/udp.c:1702
do_sock_setsockopt+0x222/0x480 net/socket.c:2329
__sys_setsockopt+0x1a4/0x270 net/socket.c:2352
__do_sys_setsockopt net/socket.c:2361 [inline]
__se_sys_setsockopt net/socket.c:2358 [inline]
__x64_sys_setsockopt+0xbd/0x160 net/socket.c:2358
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 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_INET6 --> &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_INET6);

*** DEADLOCK ***

1 lock held by syz-executor308/20073:
#0: ffffffff8fac31e8 (rtnl_mutex){+.+.}-{3:3}, at: do_ipv6_setsockopt+0x1f4d/0x4800 net/ipv6/ipv6_sockglue.c:566

stack backtrace:
CPU: 1 UID: 0 PID: 20073 Comm: syz-executor308 Not tainted 6.12.0-rc2-syzkaller-00058-g75b607fab38d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_circular_bug+0x419/0x5d0 kernel/locking/lockdep.c:2074
check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2206
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain kernel/locking/lockdep.c:3904 [inline]
__lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5202
lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
lock_sock_nested+0x3a/0xf0 net/core/sock.c:3611
lock_sock include/net/sock.h:1609 [inline]
sockopt_lock_sock net/core/sock.c:1125 [inline]
sockopt_lock_sock+0x54/0x70 net/core/sock.c:1116
do_ipv6_setsockopt+0x1f55/0x4800 net/ipv6/ipv6_sockglue.c:567
ipv6_setsockopt+0xcb/0x170 net/ipv6/ipv6_sockglue.c:993
udpv6_setsockopt+0x7d/0xd0 net/ipv6/udp.c:1702
do_sock_setsockopt+0x222/0x480 net/socket.c:2329
__sys_setsockopt+0x1a4/0x270 net/socket.c:2352
__do_sys_setsockopt net/socket.c:2361 [inline]
__se_sys_setsockopt net/socket.c:2358 [inline]
__x64_sys_setsockopt+0xbd/0x160 net/socket.c:2358
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3b71d4e8a9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 18 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f3b71ce7198 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f3b71dd93d8 RCX: 00007f3b71d4e8a9
RDX: 000000000000001b RSI: 0000000000000029 RDI: 0000000000000003
RBP: 00007f3b71dd93d0 R08: 000000000000056b R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3b71da6410
R13: 00007f3b71ce71a0 R14: 80000000000000df R15: 00007f3b71da601d
</TASK>

---
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#syz test: git://repo/address.git branch-or-commit-hash
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Next message: patchwork-bot+netdevbpf: "Re: [PATCH net] net: hns3/hns: Update the maintainer for the HNS3/HNS ethernet driver"
Previous message: FUJITA Tomonori: "Re: [PATCH net-next v2 3/6] rust: time: Implement addition of Ktime and Delta"
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