Hello, syzbot found the following issue on: HEAD commit: 743ff02152bc ethtool: Don't check for NULL info in prepare.. git tree: net-next console+strace: https://syzkaller.appspot.com/x/log.txt?x=146ac8d3980000 kernel config: https://syzkaller.appspot.com/x/.config?x=5efb917b1462a973 dashboard link: https://syzkaller.appspot.com/bug?extid=ad601904231505ad6617 compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=131875c9980000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1741f94b980000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/69cb8d5cd046/disk-743ff021.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/8f52c95a23c5/vmlinux-743ff021.xz kernel image: https://storage.googleapis.com/syzbot-assets/93f2f40e650b/bzImage-743ff021.xz The issue was bisected to: commit c9c0ee5f20c593faf289fa8850c3ed84031dd12a Author: Breno Leitao <leitao@xxxxxxxxxx> Date: Mon Jul 29 10:47:40 2024 +0000 net: skbuff: Skip early return in skb_unref when debugging bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16b7066d980000 final oops: https://syzkaller.appspot.com/x/report.txt?x=15b7066d980000 console output: https://syzkaller.appspot.com/x/log.txt?x=11b7066d980000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+ad601904231505ad6617@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: c9c0ee5f20c5 ("net: skbuff: Skip early return in skb_unref when debugging") ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 5233 at lib/refcount.c:28 refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28 Modules linked in: CPU: 0 UID: 0 PID: 5233 Comm: syz-executor339 Not tainted 6.10.0-syzkaller-12610-g743ff02152bc #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024 RIP: 0010:refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28 Code: 00 17 40 8c e8 67 97 a5 fc 90 0f 0b 90 90 eb 99 e8 1b 89 e3 fc c6 05 76 7d 31 0b 01 90 48 c7 c7 60 17 40 8c e8 47 97 a5 fc 90 <0f> 0b 90 90 e9 76 ff ff ff e8 f8 88 e3 fc c6 05 50 7d 31 0b 01 90 RSP: 0018:ffffc900000076a0 EFLAGS: 00010246 RAX: adacdd6de1fa9d00 RBX: ffff88802c47c224 RCX: ffff8880234fda00 RDX: 0000000080000101 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000003 R08: ffffffff81559432 R09: 1ffff1101724519a R10: dffffc0000000000 R11: ffffed101724519b R12: ffff88807d01a468 R13: ffff88802c47c224 R14: 1ffff1100fa03498 R15: ffff88807d01a400 FS: 0000555569709380(0000) GS:ffff8880b9200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000000 CR3: 000000001eb56000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> kfree_skb_reason include/linux/skbuff.h:1260 [inline] kfree_skb include/linux/skbuff.h:1269 [inline] j1939_session_destroy net/can/j1939/transport.c:282 [inline] __j1939_session_release net/can/j1939/transport.c:294 [inline] kref_put include/linux/kref.h:65 [inline] j1939_session_put+0x1e7/0x440 net/can/j1939/transport.c:299 j1939_tp_cmd_recv net/can/j1939/transport.c:2113 [inline] j1939_tp_recv+0x7fe/0x1050 net/can/j1939/transport.c:2161 j1939_can_recv+0x732/0xb20 net/can/j1939/main.c:108 deliver net/can/af_can.c:572 [inline] can_rcv_filter+0x359/0x7f0 net/can/af_can.c:606 can_receive+0x31c/0x470 net/can/af_can.c:663 can_rcv+0x144/0x260 net/can/af_can.c:687 __netif_receive_skb_one_core net/core/dev.c:5660 [inline] __netif_receive_skb+0x2e0/0x650 net/core/dev.c:5774 process_backlog+0x662/0x15b0 net/core/dev.c:6107 __napi_poll+0xcb/0x490 net/core/dev.c:6771 napi_poll net/core/dev.c:6840 [inline] net_rx_action+0x89b/0x1240 net/core/dev.c:6962 handle_softirqs+0x2c4/0x970 kernel/softirq.c:554 __do_softirq kernel/softirq.c:588 [inline] invoke_softirq kernel/softirq.c:428 [inline] __irq_exit_rcu+0xf4/0x1c0 kernel/softirq.c:637 irq_exit_rcu+0x9/0x30 kernel/softirq.c:649 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702 RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline] RIP: 0010:_raw_spin_unlock_irqrestore+0xd8/0x140 kernel/locking/spinlock.c:194 Code: 9c 8f 44 24 20 42 80 3c 23 00 74 08 4c 89 f7 e8 0e 9c 3b f6 f6 44 24 21 02 75 52 41 f7 c7 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 63 c1 a3 f5 65 8b 05 64 b7 44 74 85 c0 74 43 48 c7 04 24 0e 36 RSP: 0018:ffffc900035378c0 EFLAGS: 00000206 RAX: adacdd6de1fa9d00 RBX: 1ffff920006a6f1c RCX: ffffffff81701f3a RDX: dffffc0000000000 RSI: ffffffff8bead5a0 RDI: 0000000000000001 RBP: ffffc90003537950 R08: ffffffff9351e8e7 R09: 1ffffffff26a3d1c R10: dffffc0000000000 R11: fffffbfff26a3d1d R12: dffffc0000000000 R13: 1ffff920006a6f18 R14: ffffc900035378e0 R15: 0000000000000246 j1939_sk_send_loop net/can/j1939/socket.c:1164 [inline] j1939_sk_sendmsg+0xe01/0x14c0 net/can/j1939/socket.c:1277 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:745 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597 ___sys_sendmsg net/socket.c:2651 [inline] __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2680 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fd558d90e09 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 01 1a 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe518919c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fd558d90e09 RDX: 0000000000000000 RSI: 0000000020000280 RDI: 0000000000000003 RBP: 00000000000f4240 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe51891a20 R13: 00007fd558dde406 R14: 0000000000000003 R15: 00007ffe51891a00 </TASK> ---------------- Code disassembly (best guess): 0: 9c pushf 1: 8f 44 24 20 pop 0x20(%rsp) 5: 42 80 3c 23 00 cmpb $0x0,(%rbx,%r12,1) a: 74 08 je 0x14 c: 4c 89 f7 mov %r14,%rdi f: e8 0e 9c 3b f6 call 0xf63b9c22 14: f6 44 24 21 02 testb $0x2,0x21(%rsp) 19: 75 52 jne 0x6d 1b: 41 f7 c7 00 02 00 00 test $0x200,%r15d 22: 74 01 je 0x25 24: fb sti 25: bf 01 00 00 00 mov $0x1,%edi * 2a: e8 63 c1 a3 f5 call 0xf5a3c192 <-- trapping instruction 2f: 65 8b 05 64 b7 44 74 mov %gs:0x7444b764(%rip),%eax # 0x7444b79a 36: 85 c0 test %eax,%eax 38: 74 43 je 0x7d 3a: 48 rex.W 3b: c7 .byte 0xc7 3c: 04 24 add $0x24,%al 3e: 0e (bad) 3f: 36 ss --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup
