==================================================================
BUG: KASAN: slab-use-after-free in dvb_device_open+0xc4/0x340
Read of size 8 at addr ffff88810b899c18 by task syz.8.998/10538

CPU: 1 UID: 0 PID: 10538 Comm: syz.8.998 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_address_description+0x55/0x1e0
 print_report+0x58/0x70
 kasan_report+0x117/0x150
 dvb_device_open+0xc4/0x340
 chrdev_open+0x4d9/0x600
 do_dentry_open+0x816/0x1380
 vfs_open+0x3b/0x340
 path_openat+0x2e44/0x3830
 do_file_open+0x23e/0x4a0
 do_sys_openat2+0x115/0x200
 __x64_sys_openat+0x138/0x170
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f29e9d5e90e
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:00007f29e7fd4b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f29e7fd56c0 RCX: 00007f29e9d5e90e
RDX: 0000000000000801 RSI: 00007f29e7fd4c00 RDI: ffffffffffffff9c
RBP: 00007f29e7fd4c00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: cccccccccccccccd
R13: 00007f29ea026128 R14: 00007f29ea026090 R15: 00007ffda7a4c038
 </TASK>

Allocated by task 10212:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_noprof+0x375/0x720
 iter_file_splice_write+0x1ea/0x1240
 direct_splice_actor+0x101/0x160
 splice_direct_to_actor+0x57b/0xcb0
 do_splice_direct+0x195/0x290
 do_sendfile+0x52e/0x7c0
 __se_sys_sendfile64+0xdf/0x1a0
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 10212:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x40/0x50
 __kasan_slab_free+0x5c/0x80
 kfree+0x1c5/0x640
 iter_file_splice_write+0x109f/0x1240
 direct_splice_actor+0x101/0x160
 splice_direct_to_actor+0x57b/0xcb0
 do_splice_direct+0x195/0x290
 do_sendfile+0x52e/0x7c0
 __se_sys_sendfile64+0xdf/0x1a0
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88810b899c00
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 24 bytes inside of
 freed 256-byte region [ffff88810b899c00, ffff88810b899d00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88810b899c00 pfn:0x10b898
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x17ff00000000240(workingset|head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 017ff00000000240 ffff888100041b40 ffffea000440c290 ffffea00042ce490
raw: ffff88810b899c00 000000080010000f 00000000f5000000 0000000000000000
head: 017ff00000000240 ffff888100041b40 ffffea000440c290 ffffea00042ce490
head: ffff88810b899c00 000000080010000f 00000000f5000000 0000000000000000
head: 017ff00000000001 ffffffffffffff81 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 12443758284
 post_alloc_hook+0x1f9/0x250
 get_page_from_freelist+0x2205/0x2280
 __alloc_frozen_pages_noprof+0x217/0x5a0
 allocate_slab+0x7c/0x5e0
 refill_objects+0x2d5/0x350
 __pcs_replace_empty_main+0x2bf/0x6b0
 __kmalloc_cache_noprof+0x3a7/0x660
 bus_add_driver+0x162/0x670
 driver_register+0x23a/0x320
 usb_register_driver+0x1e4/0x390
 do_one_initcall+0x250/0x870
 do_initcall_level+0x10a/0x1a0
 do_initcalls+0x59/0xa0
 kernel_init_freeable+0x29d/0x3e0
 kernel_init+0x1d/0x1d0
 ret_from_fork+0x514/0xb70
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88810b899b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88810b899b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88810b899c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88810b899c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810b899d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
