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BUG: KASAN: slab-out-of-bounds in blk_mq_free_rqs+0xea/0x680 block/blk-mq.c:-1
Read of size 8 at addr ffff888026af5ac8 by task syz.7.5807/23927

CPU: 1 UID: 0 PID: 23927 Comm: syz.7.5807 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 blk_mq_free_rqs+0xea/0x680 block/blk-mq.c:-1
 blk_mq_free_map_and_rqs+0x40/0xf0 block/blk-mq.c:4157
 blk_mq_free_sched_tags block/blk-mq-sched.c:425 [inline]
 blk_mq_free_sched_res+0xeb/0x280 block/blk-mq-sched.c:436
 elevator_change_done+0x1d2/0x5f0 block/elevator.c:639
 elevator_change+0x321/0x450 block/elevator.c:685
 elevator_set_none+0xb5/0x140 block/elevator.c:769
 blk_mq_elv_switch_none block/blk-mq.c:5110 [inline]
 __blk_mq_update_nr_hw_queues block/blk-mq.c:5155 [inline]
 blk_mq_update_nr_hw_queues+0x607/0x1a80 block/blk-mq.c:5220
 nbd_start_device+0x17f/0xb20 drivers/block/nbd.c:1489
 nbd_start_device_ioctl drivers/block/nbd.c:1548 [inline]
 __nbd_ioctl drivers/block/nbd.c:1623 [inline]
 nbd_ioctl+0x57b/0xe40 drivers/block/nbd.c:1663
 blkdev_ioctl+0x5e6/0x750 block/ioctl.c:804
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2d1d40c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2d1b666028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f2d1d685fa0 RCX: 00007f2d1d40c799
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003
RBP: 00007f2d1d4a2c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2d1d686038 R14: 00007f2d1d685fa0 R15: 00007ffd1fc5bc68
 </TASK>

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5260 [inline]
 __kmalloc_node_noprof+0x377/0x7f0 mm/slub.c:5266
 kmalloc_array_node_noprof include/linux/slab.h:1169 [inline]
 blk_mq_alloc_tag_set+0x4e3/0xfc0 block/blk-mq.c:4903
 nbd_dev_add+0x30e/0xb50 drivers/block/nbd.c:1933
 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
 do_one_initcall+0x250/0x8d0 init/main.c:1382
 do_initcall_level+0x104/0x190 init/main.c:1444
 do_initcalls+0x59/0xa0 init/main.c:1460
 kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
 kernel_init+0x1d/0x1d0 init/main.c:1582
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888026af5ac0
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes to the right of
 allocated 8-byte region [ffff888026af5ac0, ffff888026af5ac8)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888026af52a0 pfn:0x26af5
flags: 0x80000000000200(workingset|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000200 ffff88813fe1c500 ffffea0000986bd0 ffffea00017d0a90
raw: ffff888026af52a0 000000080080006a 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 7870120357, free_ts 7754242987
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
 prep_new_page mm/page_alloc.c:1897 [inline]
 get_page_from_freelist+0x28bb/0x2950 mm/page_alloc.c:3962
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
 alloc_slab_page mm/slub.c:3292 [inline]
 allocate_slab+0x77/0x660 mm/slub.c:3481
 new_slab mm/slub.c:3539 [inline]
 refill_objects+0x334/0x3c0 mm/slub.c:7175
 refill_sheaf mm/slub.c:2812 [inline]
 __pcs_replace_empty_main+0x35c/0x710 mm/slub.c:4615
 alloc_from_pcs mm/slub.c:4717 [inline]
 slab_alloc_node mm/slub.c:4851 [inline]
 __do_kmalloc_node mm/slub.c:5259 [inline]
 __kmalloc_node_noprof+0x610/0x7f0 mm/slub.c:5266
 kmalloc_array_node_noprof include/linux/slab.h:1169 [inline]
 blk_mq_alloc_tag_set+0x4e3/0xfc0 block/blk-mq.c:4903
 nbd_dev_add+0x30e/0xb50 drivers/block/nbd.c:1933
 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
 do_one_initcall+0x250/0x8d0 init/main.c:1382
 do_initcall_level+0x104/0x190 init/main.c:1444
 do_initcalls+0x59/0xa0 init/main.c:1460
 kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
 kernel_init+0x1d/0x1d0 init/main.c:1582
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
page last free pid 10 tgid 10 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xfe3/0x1170 mm/page_alloc.c:2978
 vfree+0x2ac/0x470 mm/vmalloc.c:3479
 delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3398
 process_one_work kernel/workqueue.c:3276 [inline]
 process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff888026af5980: 06 fc fc fc fa fc fc fc 05 fc fc fc 07 fc fc fc
 ffff888026af5a00: 05 fc fc fc 05 fc fc fc 05 fc fc fc 00 fc fc fc
>ffff888026af5a80: 05 fc fc fc 00 fc fc fc 00 fc fc fc 07 fc fc fc
                                              ^
 ffff888026af5b00: 07 fc fc fc 07 fc fc fc fa fc fc fc fa fc fc fc
 ffff888026af5b80: fa fc fc fc fa fc fc fc fa fc fc fc 02 fc fc fc
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