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006d021491bc7-6949b713b91mr2526615eaf.57.1776827042294; Tue, 21 Apr 2026 20:04:02 -0700 (PDT) Date: Tue, 21 Apr 2026 20:04:02 -0700 In-Reply-To: <20260422021327.16934-1-kartikey406@gmail.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69e83aa2.a00a0220.17a17.0021.GAE@google.com> Subject: Re: [syzbot] [net?] kernel BUG in pn_socket_sendmsg From: syzbot To: kartikey406@gmail.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: possible deadlock in __sk_receive_skb ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz-executor150/8596 is trying to acquire lock: ffff888039b2c8a0 (slock-AF_PHONET/1){+.+.}-{3:3}, at: __sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563 but task is already holding lock: ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline] ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: __sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (slock-AF_PHONET){+...}-{3:3}: rt_spin_lock+0x83/0x400 kernel/locking/spinlock_rt.c:56 spin_lock include/linux/spinlock_rt.h:45 [inline] __sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565 sk_receive_skb include/net/sock.h:2022 [inline] phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1 __netif_receive_skb_one_core net/core/dev.c:6210 [inline] __netif_receive_skb net/core/dev.c:6323 [inline] process_backlog+0x5e1/0xc60 net/core/dev.c:6674 __napi_poll+0xab/0x550 net/core/dev.c:7738 napi_poll net/core/dev.c:7801 [inline] net_rx_action+0x696/0xe00 net/core/dev.c:7958 handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626 __do_softirq kernel/softirq.c:660 [inline] __local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302 local_bh_enable include/linux/bottom_half.h:33 [inline] netif_rx+0xb9/0xf0 net/core/dev.c:5776 pn_send+0x62a/0x8e0 net/phonet/af_phonet.c:188 pn_skb_send+0x218/0x530 net/phonet/af_phonet.c:275 pep_indicate net/phonet/pep.c:123 [inline] pipe_snd_status+0x1f1/0x320 net/phonet/pep.c:221 pipe_grant_credits net/phonet/pep.c:244 [inline] pipe_do_rcv+0xf15/0x16a0 net/phonet/pep.c:433 sk_backlog_rcv include/net/sock.h:1190 [inline] __sk_receive_skb+0x962/0x9e0 net/core/sock.c:572 sk_receive_skb include/net/sock.h:2022 [inline] pep_do_rcv+0x685/0xaa0 net/phonet/pep.c:675 sk_backlog_rcv include/net/sock.h:1190 [inline] __release_sock+0x2a9/0x3d0 net/core/sock.c:3216 release_sock+0x1be/0x290 net/core/sock.c:3815 pep_sock_accept+0xd47/0x11e0 net/phonet/pep.c:879 pn_socket_accept+0xc1/0x310 net/phonet/socket.c:303 do_accept+0x6ca/0x930 net/socket.c:2062 __sys_accept4_file net/socket.c:2096 [inline] __sys_accept4+0x139/0x230 net/socket.c:2118 __do_sys_accept4 net/socket.c:2125 [inline] __se_sys_accept4 net/socket.c:2122 [inline] __x64_sys_accept4+0x9a/0xb0 net/socket.c:2122 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (slock-AF_PHONET/1){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3167 [inline] check_prevs_add kernel/locking/lockdep.c:3286 [inline] validate_chain kernel/locking/lockdep.c:3910 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5239 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870 rt_spin_lock_nested+0x81/0x3f0 kernel/locking/spinlock_rt.c:64 __sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563 sk_receive_skb include/net/sock.h:2022 [inline] pep_do_rcv+0x685/0xaa0 net/phonet/pep.c:675 sk_backlog_rcv include/net/sock.h:1190 [inline] __sk_receive_skb+0x962/0x9e0 net/core/sock.c:572 sk_receive_skb include/net/sock.h:2022 [inline] phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1 __netif_receive_skb_one_core net/core/dev.c:6210 [inline] __netif_receive_skb net/core/dev.c:6323 [inline] process_backlog+0x5e1/0xc60 net/core/dev.c:6674 __napi_poll+0xab/0x550 net/core/dev.c:7738 napi_poll net/core/dev.c:7801 [inline] net_rx_action+0x696/0xe00 net/core/dev.c:7958 handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626 __do_softirq kernel/softirq.c:660 [inline] __local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302 local_bh_enable include/linux/bottom_half.h:33 [inline] netif_rx+0xb9/0xf0 net/core/dev.c:5776 pn_send+0x62a/0x8e0 net/phonet/af_phonet.c:188 pn_skb_send+0x218/0x530 net/phonet/af_phonet.c:275 pep_sock_close+0x2c1/0x5b0 include/linux/skbuff.h:-1 pn_socket_release+0x9b/0xc0 net/phonet/socket.c:34 __sock_release+0xb9/0x250 net/socket.c:726 sock_close+0x1c/0x30 net/socket.c:1529 __fput+0x461/0xa70 fs/file_table.c:510 fput_close_sync+0x11f/0x240 fs/file_table.c:615 __do_sys_close fs/open.c:1507 [inline] __se_sys_close fs/open.c:1492 [inline] __x64_sys_close+0x7e/0x110 fs/open.c:1492 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(slock-AF_PHONET); lock(slock-AF_PHONET/1); lock(slock-AF_PHONET); lock(slock-AF_PHONET/1); *** DEADLOCK *** 7 locks held by syz-executor150/8596: #0: ffff88805a1fc638 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1029 [inline] #0: ffff88805a1fc638 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: __sock_release+0x89/0x250 net/socket.c:725 #1: ffff888039b2dad8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline] #1: ffff888039b2dad8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: pep_sock_close+0x86/0x5b0 net/phonet/pep.c:742 #2: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163 #3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: process_backlog+0x271/0xc60 net/core/dev.c:6673 #4: ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline] #4: ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: __sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565 #5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline] #5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1e0/0x400 kernel/locking/spinlock_rt.c:57 #6: ffff888034c5b7d8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: sk_receive_skb include/net/sock.h:2022 [inline] #6: ffff888034c5b7d8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1 stack backtrace: CPU: 0 UID: 0 PID: 8596 Comm: syz-executor150 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2045 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2177 check_prev_add kernel/locking/lockdep.c:3167 [inline] check_prevs_add kernel/locking/lockdep.c:3286 [inline] validate_chain kernel/locking/lockdep.c:3910 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5239 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870 rt_spin_lock_nested+0x81/0x3f0 kernel/locking/spinlock_rt.c:64 __sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563 sk_receive_skb include/net/sock.h:2022 [inline] pep_do_rcv+0x685/0xaa0 net/phonet/pep.c:675 sk_backlog_rcv include/net/sock.h:1190 [inline] __sk_receive_skb+0x962/0x9e0 net/core/sock.c:572 sk_receive_skb include/net/sock.h:2022 [inline] phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1 __netif_receive_skb_one_core net/core/dev.c:6210 [inline] __netif_receive_skb net/core/dev.c:6323 [inline] process_backlog+0x5e1/0xc60 net/core/dev.c:6674 __napi_poll+0xab/0x550 net/core/dev.c:7738 napi_poll net/core/dev.c:7801 [inline] net_rx_action+0x696/0xe00 net/core/dev.c:7958 handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626 __do_softirq kernel/softirq.c:660 [inline] __local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302 local_bh_enable include/linux/bottom_half.h:33 [inline] netif_rx+0xb9/0xf0 net/core/dev.c:5776 pn_send+0x62a/0x8e0 net/phonet/af_phonet.c:188 pn_skb_send+0x218/0x530 net/phonet/af_phonet.c:275 pep_sock_close+0x2c1/0x5b0 include/linux/skbuff.h:-1 pn_socket_release+0x9b/0xc0 net/phonet/socket.c:34 __sock_release+0xb9/0x250 net/socket.c:726 sock_close+0x1c/0x30 net/socket.c:1529 __fput+0x461/0xa70 fs/file_table.c:510 fput_close_sync+0x11f/0x240 fs/file_table.c:615 __do_sys_close fs/open.c:1507 [inline] __se_sys_close fs/open.c:1492 [inline] __x64_sys_close+0x7e/0x110 fs/open.c:1492 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fd3c4acf98e Code: 08 0f 85 65 e1 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08 RSP: 002b:00007ffcc0cf80b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: ffffffffffffffda RBX: 00005555771d0400 RCX: 00007fd3c4acf98e RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005 RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000077f63 R13: 0000000000077f95 R14: 00007fd3c4b6ab6c R15: 00007fd3c4b6ab60 Tested on: commit: bee6ea30 Add linux-next specific files for 20260421 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=124bd702580000 kernel config: https://syzkaller.appspot.com/x/.config?x=354b135d724a721f dashboard link: https://syzkaller.appspot.com/bug?extid=706f5eb79044e686c794 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 patch: https://syzkaller.appspot.com/x/patch.diff?x=17c45f16580000