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BUG: KASAN: slab-use-after-free in v4l2_open+0x395/0x3a0
Read of size 4 at addr ffff8881a6884860 by task v4l_id/24523

CPU: 0 UID: 0 PID: 24523 Comm: v4l_id 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
 v4l2_open+0x395/0x3a0
 chrdev_open+0x4cd/0x5e0
 do_dentry_open+0x822/0x13a0
 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+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f76be5169a4
Code: 24 20 48 8d 44 24 30 48 89 44 24 28 64 8b 04 25 18 00 00 00 85 c0 75 2c 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 76 60 48 8b 15 55 a4 0d 00 f7 d8 64 89 02 48 83
RSP: 002b:00007ffcd8258e50 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007ffcd8259068 RCX: 00007f76be5169a4
RDX: 0000000000000000 RSI: 00007ffcd825af1b RDI: 00000000ffffff9c
RBP: 00007ffcd825af1b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffcd8259080 R14: 0000563bf041a670 R15: 00007f76bea46a80
 </TASK>

Allocated by task 6199:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_cache_noprof+0x31c/0x660
 em28xx_v4l2_init+0x10b/0x2eb0
 em28xx_init_extension+0x120/0x1c0
 process_scheduled_works+0xb5d/0x1860
 worker_thread+0xa53/0xfc0
 kthread+0x389/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30

Freed by task 6199:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x46/0x50
 __kasan_slab_free+0x5c/0x80
 kfree+0x1c5/0x640
 em28xx_v4l2_init+0x1685/0x2eb0
 em28xx_init_extension+0x120/0x1c0
 process_scheduled_works+0xb5d/0x1860
 worker_thread+0xa53/0xfc0
 kthread+0x389/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30

The buggy address belongs to the object at ffff8881a6884000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 2144 bytes inside of
 freed 8192-byte region [ffff8881a6884000, ffff8881a6886000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1a6880
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff888100042280 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 057ff00000000040 ffff888100042280 dead000000000100 dead000000000122
head: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 057ff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd28c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5362, tgid 5362 (dhcpcd), ts 1009619487707, free_ts 1009618503342
 post_alloc_hook+0x1f9/0x250
 get_page_from_freelist+0x2367/0x23f0
 __alloc_frozen_pages_noprof+0x18d/0x380
 allocate_slab+0x77/0x660
 refill_objects+0x339/0x3d0
 __pcs_replace_empty_main+0x321/0x720
 __kmalloc_node_track_caller_noprof+0x572/0x7b0
 __alloc_skb+0x2c1/0x7d0
 netlink_dump+0x18d/0xe10
 netlink_recvmsg+0x690/0xa50
 sock_recvmsg+0x172/0x1b0
 ____sys_recvmsg+0x1e6/0x4a0
 ___sys_recvmsg+0x215/0x590
 __x64_sys_recvmsg+0x1ba/0x2a0
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5362 tgid 5362 stack trace:
 __free_frozen_pages+0xc2a/0xd20
 __slab_free+0x274/0x2c0
 qlist_free_all+0x99/0x100
 kasan_quarantine_reduce+0x148/0x160
 __kasan_slab_alloc+0x22/0x80
 kmem_cache_alloc_node_noprof+0x384/0x690
 __alloc_skb+0x27d/0x7d0
 netlink_sendmsg+0x5d4/0xb40
 __sys_sendto+0x672/0x710
 __x64_sys_sendto+0xde/0x100
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8881a6884700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881a6884780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881a6884800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff8881a6884880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881a6884900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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