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BUG: KASAN: slab-use-after-free in dvb_device_open+0xc4/0x350
Read of size 8 at addr ffff88810b4b7018 by task syz.7.1492/12340

CPU: 1 UID: 0 PID: 12340 Comm: syz.7.1492 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_report+0xba/0x230
 kasan_report+0x117/0x150
 dvb_device_open+0xc4/0x350
 chrdev_open+0x4cd/0x5e0
 do_dentry_open+0x785/0x14e0
 vfs_open+0x3b/0x340
 path_openat+0x2e08/0x3860
 do_file_open+0x23e/0x4a0
 do_sys_openat2+0x113/0x200
 __x64_sys_openat+0x138/0x170
 do_syscall_64+0x14d/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f371b95d04e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007f371c7d7b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f371c7d86c0 RCX: 00007f371b95d04e
RDX: 0000000000000002 RSI: 00007f371c7d7c00 RDI: ffffffffffffff9c
RBP: 00007f371c7d7c00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: cccccccccccccccd
R13: 00007f371bc16128 R14: 00007f371bc16090 R15: 00007fffba2038e8
 </TASK>

Allocated by task 12311:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_cache_noprof+0x31c/0x660
 __se_sys_memfd_create+0x21d/0x410
 do_syscall_64+0x14d/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 12311:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x46/0x50
 __kasan_slab_free+0x5c/0x80
 kfree+0x1c1/0x630
 __se_sys_memfd_create+0x2e2/0x410
 do_syscall_64+0x14d/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88810b4b7000
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 24 bytes inside of
 freed 256-byte region [ffff88810b4b7000, ffff88810b4b7100)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10b4b6
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x17ff00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 017ff00000000040 ffff888100041b40 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 017ff00000000040 ffff888100041b40 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 017ff00000000001 ffffea00042d2d81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 18349755278, free_ts 16830968845
 post_alloc_hook+0x231/0x280
 get_page_from_freelist+0x24dc/0x2580
 __alloc_frozen_pages_noprof+0x18d/0x380
 allocate_slab+0x77/0x660
 refill_objects+0x331/0x3c0
 __pcs_replace_empty_main+0x2e6/0x730
 __kmalloc_cache_noprof+0x392/0x660
 bus_add_driver+0x162/0x670
 driver_register+0x23a/0x320
 usb_register_driver+0x1e4/0x390
 do_one_initcall+0x250/0x8d0
 do_initcall_level+0x104/0x190
 do_initcalls+0x59/0xa0
 kernel_init_freeable+0x2a6/0x3e0
 kernel_init+0x1d/0x1d0
 ret_from_fork+0x51e/0xb90
page last free pid 33 tgid 33 stack trace:
 __free_frozen_pages+0xc2b/0xdb0
 vfree+0x25a/0x400
 delayed_vfree_work+0x55/0x80
 process_scheduled_works+0xb6e/0x18c0
 worker_thread+0xa53/0xfc0
 kthread+0x388/0x470
 ret_from_fork+0x51e/0xb90
 ret_from_fork_asm+0x1a/0x30

Memory state around the buggy address:
 ffff88810b4b6f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88810b4b6f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88810b4b7000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88810b4b7080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810b4b7100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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