------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 2 PID: 28686 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28 Modules linked in: CPU: 2 UID: 0 PID: 28686 Comm: syz.1.6517 Not tainted 6.14.0-rc7-syzkaller-00186-gd07de43e3f05 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28 Code: ff 89 de e8 e8 34 f7 fc 84 db 0f 85 66 ff ff ff e8 3b 3a f7 fc c6 05 ef 62 88 0b 01 90 48 c7 c7 e0 06 d3 8b e8 27 6b b7 fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 18 3a f7 fc 0f b6 1d ca 62 88 0b 31 RSP: 0018:ffffc90003a9f9b8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000cd11000 RDX: 0000000000080000 RSI: ffffffff817a2276 RDI: 0000000000000001 RBP: ffff88806811e8d0 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000001 R13: 0000000000000000 R14: ffff88806811e8d0 R15: ffff88804ffc6000 FS: 0000000000000000(0000) GS:ffff88802b600000(0063) knlGS:00000000f50f6b40 CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 CR2: 00000000f73ad194 CR3: 000000004dd04000 CR4: 0000000000352ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 Call Trace: __refcount_sub_and_test include/linux/refcount.h:275 [inline] __refcount_dec_and_test include/linux/refcount.h:307 [inline] refcount_dec_and_test include/linux/refcount.h:325 [inline] io_tx_ubuf_complete+0x236/0x280 io_uring/notif.c:50 io_notif_flush io_uring/notif.h:40 [inline] io_send_zc_cleanup+0x8a/0x1c0 io_uring/net.c:1222 io_clean_op io_uring/io_uring.c:406 [inline] io_free_batch_list io_uring/io_uring.c:1429 [inline] __io_submit_flush_completions+0xcb3/0x1df0 io_uring/io_uring.c:1470 io_submit_flush_completions io_uring/io_uring.h:159 [inline] ctx_flush_and_put.constprop.0+0x9a/0x410 io_uring/io_uring.c:1031 io_handle_tw_list+0x431/0x540 io_uring/io_uring.c:1065 tctx_task_work_run+0xac/0x390 io_uring/io_uring.c:1123 tctx_task_work+0x7b/0xd0 io_uring/io_uring.c:1141 task_work_run+0x14e/0x250 kernel/task_work.c:227 get_signal+0x1d3/0x26c0 kernel/signal.c:2809 arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop kernel/entry/common.c:111 [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+0x150/0x2a0 kernel/entry/common.c:218 __do_fast_syscall_32+0x80/0x120 arch/x86/entry/common.c:390 do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:412 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf746e579 Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 RSP: 002b:00000000f50f655c EFLAGS: 00000296 ORIG_RAX: 00000000000001aa RAX: 0000000000000800 RBX: 0000000000000003 RCX: 00000000000047bc RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 ---------------- Code disassembly (best guess), 2 bytes skipped: 0: 10 06 adc %al,(%rsi) 2: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi 6: 10 07 adc %al,(%rdi) 8: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi c: 10 08 adc %cl,(%rax) e: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi 1e: 00 51 52 add %dl,0x52(%rcx) 21: 55 push %rbp 22: 89 e5 mov %esp,%ebp 24: 0f 34 sysenter 26: cd 80 int $0x80 * 28: 5d pop %rbp <-- trapping instruction 29: 5a pop %rdx 2a: 59 pop %rcx 2b: c3 ret 2c: 90 nop 2d: 90 nop 2e: 90 nop 2f: 90 nop 30: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi 37: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi