Linux kernel crash report:
==================================================================
BUG: KASAN: use-after-free in io_wq_worker_wake+0xa8/0xb0 io_uring/io-wq.c:862
Read of size 8 at addr ffff88801cdd7028 by task syz-executor318/18434

CPU: 1 PID: 18434 Comm: syz-executor318 Not tainted 6.2.0-rc3-syzkaller-00008-g1fe4fd6f5cad #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:306 [inline]
 print_report+0x15e/0x45d mm/kasan/report.c:417
 kasan_report+0xbf/0x1f0 mm/kasan/report.c:517
 io_wq_worker_wake+0xa8/0xb0 io_uring/io-wq.c:862
 io_wq_for_each_worker io_uring/io-wq.c:849 [inline]
 io_wq_exit_workers io_uring/io-wq.c:1250 [inline]
 io_wq_put_and_exit+0x52a/0xe30 io_uring/io-wq.c:1289
 io_uring_clean_tctx+0x117/0x178 io_uring/tctx.c:193
 io_uring_cancel_generic+0x5ae/0x606 io_uring/io_uring.c:3145
 io_uring_files_cancel include/linux/io_uring.h:55 [inline]
 do_exit+0x522/0x2950 kernel/exit.c:822
 do_group_exit+0xd4/0x2a0 kernel/exit.c:1012
 get_signal+0x21c3/0x2450 kernel/signal.c:2859
 arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306
 exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
 exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296
 do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fbc7f2cbb99
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 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:00007fbc7f27d2e8 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
RAX: 00000000000002ff RBX: 00007fbc7f353428 RCX: 00007fbc7f2cbb99
RDX: 0000000000000000 RSI: 00000000000002ff RDI: 0000000000000003
RBP: 00007fbc7f353420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fbc7f35342c
R13: 00007fbc7f321074 R14: 8000000000000001 R15: 0000000000000003
 </TASK>

Allocated by task 18434:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:371 [inline]
 ____kasan_kmalloc mm/kasan/common.c:330 [inline]
 __kasan_kmalloc+0xa5/0xb0 mm/kasan/common.c:380
 kmalloc_node include/linux/slab.h:606 [inline]
 kzalloc_node include/linux/slab.h:731 [inline]
 create_io_worker+0x10c/0x630 io_uring/io-wq.c:801
 io_wqe_create_worker io_uring/io-wq.c:310 [inline]
 io_wqe_enqueue+0x6c3/0xbc0 io_uring/io-wq.c:936
 io_queue_iowq+0x282/0x5c0 io_uring/io_uring.c:475
 io_queue_sqe_fallback+0xf3/0x190 io_uring/io_uring.c:2059
 io_submit_sqe io_uring/io_uring.c:2281 [inline]
 io_submit_sqes+0x11db/0x1e60 io_uring/io_uring.c:2397
 __do_sys_io_uring_enter+0xc1d/0x2540 io_uring/io_uring.c:3345
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 18437:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x40 mm/kasan/generic.c:518
 ____kasan_slab_free mm/kasan/common.c:236 [inline]
 ____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1781 [inline]
 slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1807
 slab_free mm/slub.c:3787 [inline]
 __kmem_cache_free+0xaf/0x3b0 mm/slub.c:3800
 io_wq_cancel_tw_create io_uring/io-wq.c:1233 [inline]
 io_queue_worker_create+0x567/0x660 io_uring/io-wq.c:381
 io_wqe_dec_running+0x1e4/0x240 io_uring/io-wq.c:410
 io_wq_worker_sleeping+0xa6/0xc0 io_uring/io-wq.c:698
 sched_submit_work kernel/sched/core.c:6597 [inline]
 schedule+0x16e/0x1b0 kernel/sched/core.c:6628
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6690
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0xa48/0x1360 kernel/locking/mutex.c:747
 io_ring_submit_lock io_uring/io_uring.h:215 [inline]
 io_file_get_fixed io_uring/io_uring.c:1966 [inline]
 io_assign_file io_uring/io_uring.c:1834 [inline]
 io_assign_file io_uring/io_uring.c:1828 [inline]
 io_wq_submit_work+0x5f7/0xdc0 io_uring/io_uring.c:1916
 io_worker_handle_work+0xc41/0x1c60 io_uring/io-wq.c:587
 io_wqe_worker+0xa5b/0xe40 io_uring/io-wq.c:632
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

Last potentially related work creation:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:488
 task_work_add+0x7f/0x2c0 kernel/task_work.c:48
 io_queue_worker_create+0x41d/0x660 io_uring/io-wq.c:373
 io_wqe_dec_running+0x1e4/0x240 io_uring/io-wq.c:410
 io_wq_worker_sleeping+0xa6/0xc0 io_uring/io-wq.c:698
 sched_submit_work kernel/sched/core.c:6597 [inline]
 schedule+0x16e/0x1b0 kernel/sched/core.c:6628
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6690
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0xa48/0x1360 kernel/locking/mutex.c:747
 io_ring_submit_lock io_uring/io_uring.h:215 [inline]
 io_file_get_fixed io_uring/io_uring.c:1966 [inline]
 io_assign_file io_uring/io_uring.c:1834 [inline]
 io_assign_file io_uring/io_uring.c:1828 [inline]
 io_wq_submit_work+0x5f7/0xdc0 io_uring/io_uring.c:1916
 io_worker_handle_work+0xc41/0x1c60 io_uring/io-wq.c:587
 io_wqe_worker+0xa5b/0xe40 io_uring/io-wq.c:632
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

The buggy address belongs to the object at ffff88801cdd7000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 40 bytes inside of
 512-byte region [ffff88801cdd7000, ffff88801cdd7200)

The buggy address belongs to the physical page:
page:ffffea0000737500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1cdd4
head:ffffea0000737500 order:2 compound_mapcount:0 subpages_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffff888012441c80 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 18245, tgid 18244 (syz-executor318), ts 59882596706, free_ts 59723498525
 prep_new_page mm/page_alloc.c:2531 [inline]
 get_page_from_freelist+0x119c/0x2ce0 mm/page_alloc.c:4283
 __alloc_pages+0x1cb/0x5b0 mm/page_alloc.c:5549
 __alloc_pages_node include/linux/gfp.h:237 [inline]
 alloc_slab_page mm/slub.c:1853 [inline]
 allocate_slab+0xa7/0x350 mm/slub.c:1998
 new_slab mm/slub.c:2051 [inline]
 ___slab_alloc+0xa91/0x1400 mm/slub.c:3193
 __slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3292
 __slab_alloc_node mm/slub.c:3345 [inline]
 slab_alloc_node mm/slub.c:3442 [inline]
 __kmem_cache_alloc_node+0x1a4/0x430 mm/slub.c:3491
 kmalloc_node_trace+0x21/0x60 mm/slab_common.c:1075
 kmalloc_node include/linux/slab.h:606 [inline]
 kzalloc_node include/linux/slab.h:731 [inline]
 create_io_worker+0x10c/0x630 io_uring/io-wq.c:801
 io_wqe_create_worker io_uring/io-wq.c:310 [inline]
 io_wqe_enqueue+0x6c3/0xbc0 io_uring/io-wq.c:936
 io_queue_iowq+0x282/0x5c0 io_uring/io_uring.c:475
 io_queue_sqe_fallback+0xf3/0x190 io_uring/io_uring.c:2059
 io_submit_sqe io_uring/io_uring.c:2281 [inline]
 io_submit_sqes+0x11db/0x1e60 io_uring/io_uring.c:2397
 __do_sys_io_uring_enter+0xc1d/0x2540 io_uring/io_uring.c:3345
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1446 [inline]
 free_pcp_prepare+0x65c/0xc00 mm/page_alloc.c:1496
 free_unref_page_prepare mm/page_alloc.c:3369 [inline]
 free_unref_page+0x1d/0x490 mm/page_alloc.c:3464
 __vunmap+0x85d/0xd30 mm/vmalloc.c:2727
 free_work+0x5c/0x80 mm/vmalloc.c:100
 process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
 worker_thread+0x669/0x1090 kernel/workqueue.c:2436
 kthread+0x2e8/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

Memory state around the buggy address:
 ffff88801cdd6f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88801cdd6f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88801cdd7000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88801cdd7080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801cdd7100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Fix patch:
diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index 992dcd9f8c4c..411bb2d1acd4 100644
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -1230,7 +1230,12 @@ static void io_wq_cancel_tw_create(struct io_wq *wq)
 
 		worker = container_of(cb, struct io_worker, create_work);
 		io_worker_cancel_cb(worker);
-		kfree(worker);
+		/*
+		 * Only the worker continuation helper has worker allocated and
+		 * hence needs freeing.
+		 */
+		if (cb->func == create_worker_cont)
+			kfree(worker);
 	}
 }