| Message ID | 20250407170332.26959-1-kuniyu@amazon.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [v1,net] smc: Fix lockdep false-positive for IPPROTO_SMC. | expand |
On 4/7/25 7:03 PM, Kuniyuki Iwashima wrote: > SMC consists of two sockets: smc_sock and kernel TCP socket. > > Currently, there are two ways of creating the sockets, and syzbot reported > a lockdep splat [0] for the newer way introduced by commit d25a92ccae6b > ("net/smc: Introduce IPPROTO_SMC"). > > socket(AF_SMC , SOCK_STREAM, SMCPROTO_SMC or SMCPROTO_SMC6) > socket(AF_INET or AF_INET6, SOCK_STREAM, IPPROTO_SMC) > > When a socket is allocated, sock_lock_init() sets a lockdep lock class to > sk->sk_lock.slock based on its protocol family. In the IPPROTO_SMC case, > AF_INET or AF_INET6 lock class is assigned to smc_sock. > > The repro sets IPV6_JOIN_ANYCAST for IPv6 UDP and SMC socket and exercises > smc_switch_to_fallback() for IPPROTO_SMC. > > 1. smc_switch_to_fallback() is called under lock_sock() and holds > smc->clcsock_release_lock. > > sk_lock-AF_INET6 -> &smc->clcsock_release_lock > (sk_lock-AF_SMC) > > 2. Setting IPV6_JOIN_ANYCAST to SMC holds smc->clcsock_release_lock > and calls setsockopt() for the kernel TCP socket, which holds RTNL > and the kernel socket's lock_sock(). > > &smc->clcsock_release_lock -> rtnl_mutex (-> k-sk_lock-AF_INET6) > > 3. Setting IPV6_JOIN_ANYCAST to UDP holds RTNL and lock_sock(). > > rtnl_mutex -> sk_lock-AF_INET6 > > Then, lockdep detects a false-positive circular locking, > > .-> sk_lock-AF_INET6 -> &smc->clcsock_release_lock -> rtnl_mutex -. > `-----------------------------------------------------------------' > > but IPPROTO_SMC should have the same locking rule as AF_SMC. > > sk_lock-AF_SMC -> &smc->clcsock_release_lock -> rtnl_mutex -> k-sk_lock-AF_INET6 > > Let's set the same lock class for smc_sock. > > Given AF_SMC uses the same lock class for SMCPROTO_SMC and SMCPROTO_SMC6, > we do not need to separate the class for AF_INET and AF_INET6. > > [0]: > WARNING: possible circular locking dependency detected > 6.14.0-rc3-syzkaller-00267-gff202c5028a1 #0 Not tainted > > syz.4.1528/11571 is trying to acquire lock: > ffffffff8fef8de8 (rtnl_mutex){+.+.}-{4:4}, at: ipv6_sock_ac_close+0xd9/0x110 net/ipv6/anycast.c:220 > > but task is already holding lock: > ffff888027f596a8 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_clcsock_release+0x75/0xe0 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}: > __mutex_lock_common kernel/locking/mutex.c:585 [inline] > __mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 > smc_switch_to_fallback+0x2d/0xa00 net/smc/af_smc.c:903 > smc_sendmsg+0x13d/0x520 net/smc/af_smc.c:2781 > sock_sendmsg_nosec net/socket.c:718 [inline] > __sock_sendmsg net/socket.c:733 [inline] > ____sys_sendmsg+0xaaf/0xc90 net/socket.c:2573 > ___sys_sendmsg+0x135/0x1e0 net/socket.c:2627 > __sys_sendmsg+0x16e/0x220 net/socket.c:2659 > 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 (sk_lock-AF_INET6){+.+.}-{0:0}: > lock_sock_nested+0x3a/0xf0 net/core/sock.c:3645 > lock_sock include/net/sock.h:1624 [inline] > sockopt_lock_sock net/core/sock.c:1133 [inline] > sockopt_lock_sock+0x54/0x70 net/core/sock.c:1124 > do_ipv6_setsockopt+0x2160/0x4520 net/ipv6/ipv6_sockglue.c:567 > ipv6_setsockopt+0xcb/0x170 net/ipv6/ipv6_sockglue.c:993 > udpv6_setsockopt+0x7d/0xd0 net/ipv6/udp.c:1850 > do_sock_setsockopt+0x222/0x480 net/socket.c:2303 > __sys_setsockopt+0x1a0/0x230 net/socket.c:2328 > __do_sys_setsockopt net/socket.c:2334 [inline] > __se_sys_setsockopt net/socket.c:2331 [inline] > __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2331 > 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 (rtnl_mutex){+.+.}-{4:4}: > check_prev_add kernel/locking/lockdep.c:3163 [inline] > check_prevs_add kernel/locking/lockdep.c:3282 [inline] > validate_chain kernel/locking/lockdep.c:3906 [inline] > __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5228 > lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851 > __mutex_lock_common kernel/locking/mutex.c:585 [inline] > __mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 > ipv6_sock_ac_close+0xd9/0x110 net/ipv6/anycast.c:220 > inet6_release+0x47/0x70 net/ipv6/af_inet6.c:485 > __sock_release net/socket.c:647 [inline] > sock_release+0x8e/0x1d0 net/socket.c:675 > smc_clcsock_release+0xb7/0xe0 net/smc/smc_close.c:34 > __smc_release+0x5c2/0x880 net/smc/af_smc.c:301 > smc_release+0x1fc/0x5f0 net/smc/af_smc.c:344 > __sock_release+0xb0/0x270 net/socket.c:647 > sock_close+0x1c/0x30 net/socket.c:1398 > __fput+0x3ff/0xb70 fs/file_table.c:464 > task_work_run+0x14e/0x250 kernel/task_work.c:227 > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > exit_to_user_mode_loop kernel/entry/common.c:114 [inline] > exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > syscall_exit_to_user_mode+0x27b/0x2a0 kernel/entry/common.c:218 > do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 > 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.4.1528/11571: > #0: ffff888077e88208 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:877 [inline] > #0: ffff888077e88208 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: __sock_release+0x86/0x270 net/socket.c:646 > #1: ffff888027f596a8 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_clcsock_release+0x75/0xe0 net/smc/smc_close.c:30 > > stack backtrace: > CPU: 0 UID: 0 PID: 11571 Comm: syz.4.1528 Not tainted 6.14.0-rc3-syzkaller-00267-gff202c5028a1 #0 > 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+0x116/0x1f0 lib/dump_stack.c:120 > print_circular_bug+0x490/0x760 kernel/locking/lockdep.c:2076 > check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2208 > check_prev_add kernel/locking/lockdep.c:3163 [inline] > check_prevs_add kernel/locking/lockdep.c:3282 [inline] > validate_chain kernel/locking/lockdep.c:3906 [inline] > __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5228 > lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851 > __mutex_lock_common kernel/locking/mutex.c:585 [inline] > __mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 > ipv6_sock_ac_close+0xd9/0x110 net/ipv6/anycast.c:220 > inet6_release+0x47/0x70 net/ipv6/af_inet6.c:485 > __sock_release net/socket.c:647 [inline] > sock_release+0x8e/0x1d0 net/socket.c:675 > smc_clcsock_release+0xb7/0xe0 net/smc/smc_close.c:34 > __smc_release+0x5c2/0x880 net/smc/af_smc.c:301 > smc_release+0x1fc/0x5f0 net/smc/af_smc.c:344 > __sock_release+0xb0/0x270 net/socket.c:647 > sock_close+0x1c/0x30 net/socket.c:1398 > __fput+0x3ff/0xb70 fs/file_table.c:464 > task_work_run+0x14e/0x250 kernel/task_work.c:227 > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > exit_to_user_mode_loop kernel/entry/common.c:114 [inline] > exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > syscall_exit_to_user_mode+0x27b/0x2a0 kernel/entry/common.c:218 > do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7f8b4b38d169 > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007ffe4efd22d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 > RAX: 0000000000000000 RBX: 00000000000b14a3 RCX: 00007f8b4b38d169 > RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 > RBP: 00007f8b4b5a7ba0 R08: 0000000000000001 R09: 000000114efd25cf > R10: 00007f8b4b200000 R11: 0000000000000246 R12: 00007f8b4b5a5fac > R13: 00007f8b4b5a5fa0 R14: ffffffffffffffff R15: 00007ffe4efd23f0 > </TASK> > > Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC") > Reported-by: syzbot+be6f4b383534d88989f7@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=be6f4b383534d88989f7 > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Makes sense to me, waiting a little more to allow feedback from @Wenjia and the SMC crew. Thanks, Paolo
On 07.04.25 19:03, Kuniyuki Iwashima wrote: > SMC consists of two sockets: smc_sock and kernel TCP socket. > > Currently, there are two ways of creating the sockets, and syzbot reported > a lockdep splat [0] for the newer way introduced by commit d25a92ccae6b > ("net/smc: Introduce IPPROTO_SMC"). > > socket(AF_SMC , SOCK_STREAM, SMCPROTO_SMC or SMCPROTO_SMC6) > socket(AF_INET or AF_INET6, SOCK_STREAM, IPPROTO_SMC) > > When a socket is allocated, sock_lock_init() sets a lockdep lock class to > sk->sk_lock.slock based on its protocol family. In the IPPROTO_SMC case, > AF_INET or AF_INET6 lock class is assigned to smc_sock. > > The repro sets IPV6_JOIN_ANYCAST for IPv6 UDP and SMC socket and exercises > smc_switch_to_fallback() for IPPROTO_SMC. > > 1. smc_switch_to_fallback() is called under lock_sock() and holds > smc->clcsock_release_lock. > > sk_lock-AF_INET6 -> &smc->clcsock_release_lock > (sk_lock-AF_SMC) > > 2. Setting IPV6_JOIN_ANYCAST to SMC holds smc->clcsock_release_lock > and calls setsockopt() for the kernel TCP socket, which holds RTNL > and the kernel socket's lock_sock(). > > &smc->clcsock_release_lock -> rtnl_mutex (-> k-sk_lock-AF_INET6) > > 3. Setting IPV6_JOIN_ANYCAST to UDP holds RTNL and lock_sock(). > > rtnl_mutex -> sk_lock-AF_INET6 > > Then, lockdep detects a false-positive circular locking, > > .-> sk_lock-AF_INET6 -> &smc->clcsock_release_lock -> rtnl_mutex -. > `-----------------------------------------------------------------' > > but IPPROTO_SMC should have the same locking rule as AF_SMC. > > sk_lock-AF_SMC -> &smc->clcsock_release_lock -> rtnl_mutex -> k-sk_lock-AF_INET6 > > Let's set the same lock class for smc_sock. > > Given AF_SMC uses the same lock class for SMCPROTO_SMC and SMCPROTO_SMC6, > we do not need to separate the class for AF_INET and AF_INET6. > > [0]: > WARNING: possible circular locking dependency detected > 6.14.0-rc3-syzkaller-00267-gff202c5028a1 #0 Not tainted > > syz.4.1528/11571 is trying to acquire lock: > ffffffff8fef8de8 (rtnl_mutex){+.+.}-{4:4}, at: ipv6_sock_ac_close+0xd9/0x110 net/ipv6/anycast.c:220 > > but task is already holding lock: > ffff888027f596a8 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_clcsock_release+0x75/0xe0 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}: > __mutex_lock_common kernel/locking/mutex.c:585 [inline] > __mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 > smc_switch_to_fallback+0x2d/0xa00 net/smc/af_smc.c:903 > smc_sendmsg+0x13d/0x520 net/smc/af_smc.c:2781 > sock_sendmsg_nosec net/socket.c:718 [inline] > __sock_sendmsg net/socket.c:733 [inline] > ____sys_sendmsg+0xaaf/0xc90 net/socket.c:2573 > ___sys_sendmsg+0x135/0x1e0 net/socket.c:2627 > __sys_sendmsg+0x16e/0x220 net/socket.c:2659 > 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 (sk_lock-AF_INET6){+.+.}-{0:0}: > lock_sock_nested+0x3a/0xf0 net/core/sock.c:3645 > lock_sock include/net/sock.h:1624 [inline] > sockopt_lock_sock net/core/sock.c:1133 [inline] > sockopt_lock_sock+0x54/0x70 net/core/sock.c:1124 > do_ipv6_setsockopt+0x2160/0x4520 net/ipv6/ipv6_sockglue.c:567 > ipv6_setsockopt+0xcb/0x170 net/ipv6/ipv6_sockglue.c:993 > udpv6_setsockopt+0x7d/0xd0 net/ipv6/udp.c:1850 > do_sock_setsockopt+0x222/0x480 net/socket.c:2303 > __sys_setsockopt+0x1a0/0x230 net/socket.c:2328 > __do_sys_setsockopt net/socket.c:2334 [inline] > __se_sys_setsockopt net/socket.c:2331 [inline] > __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2331 > 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 (rtnl_mutex){+.+.}-{4:4}: > check_prev_add kernel/locking/lockdep.c:3163 [inline] > check_prevs_add kernel/locking/lockdep.c:3282 [inline] > validate_chain kernel/locking/lockdep.c:3906 [inline] > __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5228 > lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851 > __mutex_lock_common kernel/locking/mutex.c:585 [inline] > __mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 > ipv6_sock_ac_close+0xd9/0x110 net/ipv6/anycast.c:220 > inet6_release+0x47/0x70 net/ipv6/af_inet6.c:485 > __sock_release net/socket.c:647 [inline] > sock_release+0x8e/0x1d0 net/socket.c:675 > smc_clcsock_release+0xb7/0xe0 net/smc/smc_close.c:34 > __smc_release+0x5c2/0x880 net/smc/af_smc.c:301 > smc_release+0x1fc/0x5f0 net/smc/af_smc.c:344 > __sock_release+0xb0/0x270 net/socket.c:647 > sock_close+0x1c/0x30 net/socket.c:1398 > __fput+0x3ff/0xb70 fs/file_table.c:464 > task_work_run+0x14e/0x250 kernel/task_work.c:227 > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > exit_to_user_mode_loop kernel/entry/common.c:114 [inline] > exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > syscall_exit_to_user_mode+0x27b/0x2a0 kernel/entry/common.c:218 > do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 > 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.4.1528/11571: > #0: ffff888077e88208 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:877 [inline] > #0: ffff888077e88208 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: __sock_release+0x86/0x270 net/socket.c:646 > #1: ffff888027f596a8 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_clcsock_release+0x75/0xe0 net/smc/smc_close.c:30 > > stack backtrace: > CPU: 0 UID: 0 PID: 11571 Comm: syz.4.1528 Not tainted 6.14.0-rc3-syzkaller-00267-gff202c5028a1 #0 > 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+0x116/0x1f0 lib/dump_stack.c:120 > print_circular_bug+0x490/0x760 kernel/locking/lockdep.c:2076 > check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2208 > check_prev_add kernel/locking/lockdep.c:3163 [inline] > check_prevs_add kernel/locking/lockdep.c:3282 [inline] > validate_chain kernel/locking/lockdep.c:3906 [inline] > __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5228 > lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851 > __mutex_lock_common kernel/locking/mutex.c:585 [inline] > __mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 > ipv6_sock_ac_close+0xd9/0x110 net/ipv6/anycast.c:220 > inet6_release+0x47/0x70 net/ipv6/af_inet6.c:485 > __sock_release net/socket.c:647 [inline] > sock_release+0x8e/0x1d0 net/socket.c:675 > smc_clcsock_release+0xb7/0xe0 net/smc/smc_close.c:34 > __smc_release+0x5c2/0x880 net/smc/af_smc.c:301 > smc_release+0x1fc/0x5f0 net/smc/af_smc.c:344 > __sock_release+0xb0/0x270 net/socket.c:647 > sock_close+0x1c/0x30 net/socket.c:1398 > __fput+0x3ff/0xb70 fs/file_table.c:464 > task_work_run+0x14e/0x250 kernel/task_work.c:227 > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > exit_to_user_mode_loop kernel/entry/common.c:114 [inline] > exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > syscall_exit_to_user_mode+0x27b/0x2a0 kernel/entry/common.c:218 > do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7f8b4b38d169 > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007ffe4efd22d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 > RAX: 0000000000000000 RBX: 00000000000b14a3 RCX: 00007f8b4b38d169 > RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 > RBP: 00007f8b4b5a7ba0 R08: 0000000000000001 R09: 000000114efd25cf > R10: 00007f8b4b200000 R11: 0000000000000246 R12: 00007f8b4b5a5fac > R13: 00007f8b4b5a5fa0 R14: ffffffffffffffff R15: 00007ffe4efd23f0 > </TASK> > > Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC") > Reported-by: syzbot+be6f4b383534d88989f7@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=be6f4b383534d88989f7 > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Thank you for fixing it! It looks reasonable to me! Good description! Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Hello: This patch was applied to netdev/net.git (main) by Jakub Kicinski <kuba@kernel.org>: On Mon, 7 Apr 2025 10:03:17 -0700 you wrote: > SMC consists of two sockets: smc_sock and kernel TCP socket. > > Currently, there are two ways of creating the sockets, and syzbot reported > a lockdep splat [0] for the newer way introduced by commit d25a92ccae6b > ("net/smc: Introduce IPPROTO_SMC"). > > socket(AF_SMC , SOCK_STREAM, SMCPROTO_SMC or SMCPROTO_SMC6) > socket(AF_INET or AF_INET6, SOCK_STREAM, IPPROTO_SMC) > > [...] Here is the summary with links: - [v1,net] smc: Fix lockdep false-positive for IPPROTO_SMC. https://git.kernel.org/netdev/net/c/752e2217d789 You are awesome, thank you!
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 3e6cb35baf25..3760131f1484 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -362,6 +362,9 @@ static void smc_destruct(struct sock *sk) return; } +static struct lock_class_key smc_key; +static struct lock_class_key smc_slock_key; + void smc_sk_init(struct net *net, struct sock *sk, int protocol) { struct smc_sock *smc = smc_sk(sk); @@ -375,6 +378,8 @@ void smc_sk_init(struct net *net, struct sock *sk, int protocol) INIT_WORK(&smc->connect_work, smc_connect_work); INIT_DELAYED_WORK(&smc->conn.tx_work, smc_tx_work); INIT_LIST_HEAD(&smc->accept_q); + sock_lock_init_class_and_name(sk, "slock-AF_SMC", &smc_slock_key, + "sk_lock-AF_SMC", &smc_key); spin_lock_init(&smc->accept_q_lock); spin_lock_init(&smc->conn.send_lock); sk->sk_prot->hash(sk);
SMC consists of two sockets: smc_sock and kernel TCP socket. Currently, there are two ways of creating the sockets, and syzbot reported a lockdep splat [0] for the newer way introduced by commit d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC"). socket(AF_SMC , SOCK_STREAM, SMCPROTO_SMC or SMCPROTO_SMC6) socket(AF_INET or AF_INET6, SOCK_STREAM, IPPROTO_SMC) When a socket is allocated, sock_lock_init() sets a lockdep lock class to sk->sk_lock.slock based on its protocol family. In the IPPROTO_SMC case, AF_INET or AF_INET6 lock class is assigned to smc_sock. The repro sets IPV6_JOIN_ANYCAST for IPv6 UDP and SMC socket and exercises smc_switch_to_fallback() for IPPROTO_SMC. 1. smc_switch_to_fallback() is called under lock_sock() and holds smc->clcsock_release_lock. sk_lock-AF_INET6 -> &smc->clcsock_release_lock (sk_lock-AF_SMC) 2. Setting IPV6_JOIN_ANYCAST to SMC holds smc->clcsock_release_lock and calls setsockopt() for the kernel TCP socket, which holds RTNL and the kernel socket's lock_sock(). &smc->clcsock_release_lock -> rtnl_mutex (-> k-sk_lock-AF_INET6) 3. Setting IPV6_JOIN_ANYCAST to UDP holds RTNL and lock_sock(). rtnl_mutex -> sk_lock-AF_INET6 Then, lockdep detects a false-positive circular locking, .-> sk_lock-AF_INET6 -> &smc->clcsock_release_lock -> rtnl_mutex -. `-----------------------------------------------------------------' but IPPROTO_SMC should have the same locking rule as AF_SMC. sk_lock-AF_SMC -> &smc->clcsock_release_lock -> rtnl_mutex -> k-sk_lock-AF_INET6 Let's set the same lock class for smc_sock. Given AF_SMC uses the same lock class for SMCPROTO_SMC and SMCPROTO_SMC6, we do not need to separate the class for AF_INET and AF_INET6. [0]: WARNING: possible circular locking dependency detected 6.14.0-rc3-syzkaller-00267-gff202c5028a1 #0 Not tainted syz.4.1528/11571 is trying to acquire lock: ffffffff8fef8de8 (rtnl_mutex){+.+.}-{4:4}, at: ipv6_sock_ac_close+0xd9/0x110 net/ipv6/anycast.c:220 but task is already holding lock: ffff888027f596a8 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_clcsock_release+0x75/0xe0 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}: __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 smc_switch_to_fallback+0x2d/0xa00 net/smc/af_smc.c:903 smc_sendmsg+0x13d/0x520 net/smc/af_smc.c:2781 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:733 [inline] ____sys_sendmsg+0xaaf/0xc90 net/socket.c:2573 ___sys_sendmsg+0x135/0x1e0 net/socket.c:2627 __sys_sendmsg+0x16e/0x220 net/socket.c:2659 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 (sk_lock-AF_INET6){+.+.}-{0:0}: lock_sock_nested+0x3a/0xf0 net/core/sock.c:3645 lock_sock include/net/sock.h:1624 [inline] sockopt_lock_sock net/core/sock.c:1133 [inline] sockopt_lock_sock+0x54/0x70 net/core/sock.c:1124 do_ipv6_setsockopt+0x2160/0x4520 net/ipv6/ipv6_sockglue.c:567 ipv6_setsockopt+0xcb/0x170 net/ipv6/ipv6_sockglue.c:993 udpv6_setsockopt+0x7d/0xd0 net/ipv6/udp.c:1850 do_sock_setsockopt+0x222/0x480 net/socket.c:2303 __sys_setsockopt+0x1a0/0x230 net/socket.c:2328 __do_sys_setsockopt net/socket.c:2334 [inline] __se_sys_setsockopt net/socket.c:2331 [inline] __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2331 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 (rtnl_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3163 [inline] check_prevs_add kernel/locking/lockdep.c:3282 [inline] validate_chain kernel/locking/lockdep.c:3906 [inline] __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5228 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851 __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 ipv6_sock_ac_close+0xd9/0x110 net/ipv6/anycast.c:220 inet6_release+0x47/0x70 net/ipv6/af_inet6.c:485 __sock_release net/socket.c:647 [inline] sock_release+0x8e/0x1d0 net/socket.c:675 smc_clcsock_release+0xb7/0xe0 net/smc/smc_close.c:34 __smc_release+0x5c2/0x880 net/smc/af_smc.c:301 smc_release+0x1fc/0x5f0 net/smc/af_smc.c:344 __sock_release+0xb0/0x270 net/socket.c:647 sock_close+0x1c/0x30 net/socket.c:1398 __fput+0x3ff/0xb70 fs/file_table.c:464 task_work_run+0x14e/0x250 kernel/task_work.c:227 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] exit_to_user_mode_loop kernel/entry/common.c:114 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0x27b/0x2a0 kernel/entry/common.c:218 do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 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.4.1528/11571: #0: ffff888077e88208 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:877 [inline] #0: ffff888077e88208 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: __sock_release+0x86/0x270 net/socket.c:646 #1: ffff888027f596a8 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_clcsock_release+0x75/0xe0 net/smc/smc_close.c:30 stack backtrace: CPU: 0 UID: 0 PID: 11571 Comm: syz.4.1528 Not tainted 6.14.0-rc3-syzkaller-00267-gff202c5028a1 #0 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+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x490/0x760 kernel/locking/lockdep.c:2076 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2208 check_prev_add kernel/locking/lockdep.c:3163 [inline] check_prevs_add kernel/locking/lockdep.c:3282 [inline] validate_chain kernel/locking/lockdep.c:3906 [inline] __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5228 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851 __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 ipv6_sock_ac_close+0xd9/0x110 net/ipv6/anycast.c:220 inet6_release+0x47/0x70 net/ipv6/af_inet6.c:485 __sock_release net/socket.c:647 [inline] sock_release+0x8e/0x1d0 net/socket.c:675 smc_clcsock_release+0xb7/0xe0 net/smc/smc_close.c:34 __smc_release+0x5c2/0x880 net/smc/af_smc.c:301 smc_release+0x1fc/0x5f0 net/smc/af_smc.c:344 __sock_release+0xb0/0x270 net/socket.c:647 sock_close+0x1c/0x30 net/socket.c:1398 __fput+0x3ff/0xb70 fs/file_table.c:464 task_work_run+0x14e/0x250 kernel/task_work.c:227 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] exit_to_user_mode_loop kernel/entry/common.c:114 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0x27b/0x2a0 kernel/entry/common.c:218 do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f8b4b38d169 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe4efd22d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00000000000b14a3 RCX: 00007f8b4b38d169 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007f8b4b5a7ba0 R08: 0000000000000001 R09: 000000114efd25cf R10: 00007f8b4b200000 R11: 0000000000000246 R12: 00007f8b4b5a5fac R13: 00007f8b4b5a5fa0 R14: ffffffffffffffff R15: 00007ffe4efd23f0 </TASK> Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC") Reported-by: syzbot+be6f4b383534d88989f7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=be6f4b383534d88989f7 Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- net/smc/af_smc.c | 5 +++++ 1 file changed, 5 insertions(+)