====================================================== WARNING: possible circular locking dependency detected 5.7.0-rc4-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.3/31514 is trying to acquire lock: ffff88806be19668 (&u->lock/1){+.+.}-{2:2}, at: sk_diag_dump_icons net/unix/diag.c:86 [inline] ffff88806be19668 (&u->lock/1){+.+.}-{2:2}, at: sk_diag_fill.isra.0+0x9d0/0x10e0 net/unix/diag.c:154 but task is already holding lock: ffff888091bbf1e0 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:353 [inline] ffff888091bbf1e0 (rlock-AF_UNIX){+.+.}-{2:2}, at: sk_diag_dump_icons net/unix/diag.c:68 [inline] ffff888091bbf1e0 (rlock-AF_UNIX){+.+.}-{2:2}, at: sk_diag_fill.isra.0+0x8eb/0x10e0 net/unix/diag.c:154 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (rlock-AF_UNIX){+.+.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159 skb_queue_tail+0x27/0x180 net/core/skbuff.c:3143 unix_dgram_sendmsg+0xc96/0x12e0 net/unix/af_unix.c:1806 sock_sendmsg_nosec net/socket.c:652 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:672 ____sys_sendmsg+0x308/0x7e0 net/socket.c:2362 ___sys_sendmsg+0x100/0x170 net/socket.c:2416 __sys_sendmmsg+0x296/0x480 net/socket.c:2499 __compat_sys_sendmmsg net/compat.c:672 [inline] __do_compat_sys_sendmmsg net/compat.c:679 [inline] __se_compat_sys_sendmmsg net/compat.c:676 [inline] __ia32_compat_sys_sendmmsg+0x9b/0x100 net/compat.c:676 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline] do_fast_syscall_32+0x270/0xe90 arch/x86/entry/common.c:396 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 -> #0 (&u->lock/1){+.+.}-{2:2}: check_prev_add kernel/locking/lockdep.c:2515 [inline] check_prevs_add kernel/locking/lockdep.c:2620 [inline] validate_chain kernel/locking/lockdep.c:3237 [inline] __lock_acquire+0x2ab1/0x4c50 kernel/locking/lockdep.c:4355 lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4934 _raw_spin_lock_nested+0x30/0x40 kernel/locking/spinlock.c:361 sk_diag_dump_icons net/unix/diag.c:86 [inline] sk_diag_fill.isra.0+0x9d0/0x10e0 net/unix/diag.c:154 sk_diag_dump net/unix/diag.c:192 [inline] unix_diag_dump+0x441/0x550 net/unix/diag.c:220 netlink_dump+0x50b/0xf50 net/netlink/af_netlink.c:2245 __netlink_dump_start+0x63f/0x910 net/netlink/af_netlink.c:2353 netlink_dump_start include/linux/netlink.h:246 [inline] unix_diag_handler_dump+0x3ea/0x7b0 net/unix/diag.c:321 __sock_diag_cmd net/core/sock_diag.c:233 [inline] sock_diag_rcv_msg+0x2fe/0x3e0 net/core/sock_diag.c:264 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469 sock_diag_rcv+0x26/0x40 net/core/sock_diag.c:275 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline] netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329 netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918 sock_sendmsg_nosec net/socket.c:652 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:672 sock_write_iter+0x289/0x3c0 net/socket.c:1004 call_write_iter include/linux/fs.h:1907 [inline] do_iter_readv_writev+0x5a8/0x850 fs/read_write.c:694 do_iter_write fs/read_write.c:999 [inline] do_iter_write+0x18b/0x600 fs/read_write.c:980 compat_writev+0x1f1/0x390 fs/read_write.c:1352 do_compat_writev+0xd5/0x1d0 fs/read_write.c:1373 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline] do_fast_syscall_32+0x270/0xe90 arch/x86/entry/common.c:396 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(rlock-AF_UNIX); lock(&u->lock/1); lock(rlock-AF_UNIX); lock(&u->lock/1); *** DEADLOCK *** 5 locks held by syz-executor.3/31514: #0: ffffffff8a58a388 (sock_diag_mutex){+.+.}-{3:3}, at: sock_diag_rcv+0x17/0x40 net/core/sock_diag.c:274 #1: ffffffff8a58a448 (sock_diag_table_mutex){+.+.}-{3:3}, at: __sock_diag_cmd net/core/sock_diag.c:228 [inline] #1: ffffffff8a58a448 (sock_diag_table_mutex){+.+.}-{3:3}, at: sock_diag_rcv_msg+0x18d/0x3e0 net/core/sock_diag.c:264 #2: ffff888050ce1630 (nlk_cb_mutex-SOCK_DIAG){+.+.}-{3:3}, at: netlink_dump+0xd4/0xf50 net/netlink/af_netlink.c:2200 #3: ffffffff8a65df18 (unix_table_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:353 [inline] #3: ffffffff8a65df18 (unix_table_lock){+.+.}-{2:2}, at: unix_diag_dump+0x10c/0x550 net/unix/diag.c:206 #4: ffff888091bbf1e0 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:353 [inline] #4: ffff888091bbf1e0 (rlock-AF_UNIX){+.+.}-{2:2}, at: sk_diag_dump_icons net/unix/diag.c:68 [inline] #4: ffff888091bbf1e0 (rlock-AF_UNIX){+.+.}-{2:2}, at: sk_diag_fill.isra.0+0x8eb/0x10e0 net/unix/diag.c:154 stack backtrace: CPU: 0 PID: 31514 Comm: syz-executor.3 Not tainted 5.7.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x188/0x20d lib/dump_stack.c:118 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1846 check_prev_add kernel/locking/lockdep.c:2515 [inline] check_prevs_add kernel/locking/lockdep.c:2620 [inline] validate_chain kernel/locking/lockdep.c:3237 [inline] __lock_acquire+0x2ab1/0x4c50 kernel/locking/lockdep.c:4355 lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4934 _raw_spin_lock_nested+0x30/0x40 kernel/locking/spinlock.c:361 sk_diag_dump_icons net/unix/diag.c:86 [inline] sk_diag_fill.isra.0+0x9d0/0x10e0 net/unix/diag.c:154 sk_diag_dump net/unix/diag.c:192 [inline] unix_diag_dump+0x441/0x550 net/unix/diag.c:220 netlink_dump+0x50b/0xf50 net/netlink/af_netlink.c:2245 __netlink_dump_start+0x63f/0x910 net/netlink/af_netlink.c:2353 netlink_dump_start include/linux/netlink.h:246 [inline] unix_diag_handler_dump+0x3ea/0x7b0 net/unix/diag.c:321 __sock_diag_cmd net/core/sock_diag.c:233 [inline] sock_diag_rcv_msg+0x2fe/0x3e0 net/core/sock_diag.c:264 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469 sock_diag_rcv+0x26/0x40 net/core/sock_diag.c:275 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline] netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329 netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918 sock_sendmsg_nosec net/socket.c:652 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:672 sock_write_iter+0x289/0x3c0 net/socket.c:1004 call_write_iter include/linux/fs.h:1907 [inline] do_iter_readv_writev+0x5a8/0x850 fs/read_write.c:694 do_iter_write fs/read_write.c:999 [inline] do_iter_write+0x18b/0x600 fs/read_write.c:980 compat_writev+0x1f1/0x390 fs/read_write.c:1352 do_compat_writev+0xd5/0x1d0 fs/read_write.c:1373 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline] do_fast_syscall_32+0x270/0xe90 arch/x86/entry/common.c:396 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139