Hello, syzbot found the following crash on: HEAD commit: 2c523b34 Linux 5.6-rc5 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=155a5f29e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=a5295e161cd85b82 dashboard link: https://syzkaller.appspot.com/bug?extid=cea71eec5d6de256d54d compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=164b5181e00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=166dd70de00000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+cea71eec5d6de256d54d@xxxxxxxxxxxxxxxxxxxxxxxxx ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 8668 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 8668 Comm: syz-executor779 Not tainted 5.6.0-rc5-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+0x1e9/0x30e lib/dump_stack.c:118 panic+0x264/0x7a0 kernel/panic.c:221 __warn+0x209/0x210 kernel/panic.c:582 report_bug+0x1ac/0x2d0 lib/bug.c:195 fixup_bug arch/x86/kernel/traps.c:174 [inline] do_error_trap+0xca/0x1c0 arch/x86/kernel/traps.c:267 do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027 RIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28 Code: c7 e4 ff d0 88 31 c0 e8 23 20 b3 fd 0f 0b eb 85 e8 8a 4a e0 fd c6 05 ff 70 b1 05 01 48 c7 c7 10 00 d1 88 31 c0 e8 05 20 b3 fd <0f> 0b e9 64 ff ff ff e8 69 4a e0 fd c6 05 df 70 b1 05 01 48 c7 c7 RSP: 0018:ffffc90001f577d0 EFLAGS: 00010246 RAX: 8c9c9070bbb4e500 RBX: 0000000000000003 RCX: ffff8880938a63c0 RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 RBP: 0000000000000003 R08: ffffffff815e16e6 R09: fffffbfff15db92a R10: fffffbfff15db92a R11: 0000000000000000 R12: dffffc0000000000 R13: ffff88809de82000 R14: ffff8880a89237c0 R15: 1ffff11013be52b0 sctp_wfree+0x3b1/0x710 net/sctp/socket.c:9111 skb_release_head_state+0xfb/0x210 net/core/skbuff.c:651 skb_release_all net/core/skbuff.c:662 [inline] __kfree_skb+0x22/0x1c0 net/core/skbuff.c:678 sctp_chunk_destroy net/sctp/sm_make_chunk.c:1454 [inline] sctp_chunk_put+0x17b/0x200 net/sctp/sm_make_chunk.c:1481 __sctp_outq_teardown+0x80a/0x9d0 net/sctp/outqueue.c:257 sctp_association_free+0x21e/0x7c0 net/sctp/associola.c:339 sctp_cmd_delete_tcb net/sctp/sm_sideeffect.c:930 [inline] sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1318 [inline] sctp_side_effects net/sctp/sm_sideeffect.c:1185 [inline] sctp_do_sm+0x3c01/0x5560 net/sctp/sm_sideeffect.c:1156 sctp_primitive_ABORT+0x93/0xc0 net/sctp/primitive.c:104 sctp_close+0x231/0x770 net/sctp/socket.c:1512 inet_release+0x135/0x180 net/ipv4/af_inet.c:427 __sock_release net/socket.c:605 [inline] sock_close+0xd8/0x260 net/socket.c:1283 __fput+0x2d8/0x730 fs/file_table.c:280 task_work_run+0x176/0x1b0 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x5ef/0x1f80 kernel/exit.c:801 do_group_exit+0x15e/0x2c0 kernel/exit.c:899 __do_sys_exit_group+0x13/0x20 kernel/exit.c:910 __se_sys_exit_group+0x10/0x10 kernel/exit.c:908 __x64_sys_exit_group+0x37/0x40 kernel/exit.c:908 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x43ef98 Code: Bad RIP value. RSP: 002b:00007ffcc7e7c398 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043ef98 RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000 RBP: 00000000004be7a8 R08: 00000000000000e7 R09: ffffffffffffffd0 R10: 000000002059aff8 R11: 0000000000000246 R12: 0000000000000001 R13: 00000000006d01a0 R14: 0000000000000000 R15: 0000000000000000 Kernel Offset: disabled Rebooting in 86400 seconds.. --- This bug 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 bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches
